- During a cylinder compression test, Technician A says that if all cylinders read low compression, it could indicate a timing issue. Technician B says that it could be due to a widespread gasket failure. Who is correct?
- Technician A only
- Both Technician A and Technician B
- Technician B only
- Neither Technician A nor Technician B
Correct answer: Both Technician A and Technician B
The key is Both Technician A and Technician B. Technician A is right: valve timing that has slipped, such as a jumped chain or belt, holds valves off their seats at the wrong moment on every cylinder at once, so all readings fall together. Technician B is right as well: a head gasket breached across several cylinders, or a warped deck, bleeds compression from the whole engine rather than from one hole. Because each claim names a genuine engine-wide cause, Technician A only and Technician B only each credit half the picture, and Neither Technician A nor Technician B denies two sound diagnoses.
- A vehicle's engine has a rough idle and a 'check engine' light for a misfire code. The misfire is not present at higher RPMs. Which of the following could be the cause?
- A blocked element choking the induction
- A plugged converter slowing the exhaust
- A failed injector starving the cylinder
- A drifting sensor shifting the readings
Correct answer: A failed injector starving the cylinder
The key is A failed injector starving the cylinder. A dead or badly restricted injector removes fuel from one hole only, so the roughness shows at idle and is smoothed out once demand and airflow rise, and the stored code names the hole that is short. A blocked element choking the induction leans every cylinder alike and bites hardest at wide throttle rather than at idle. A plugged converter slowing the exhaust chokes the engine as flow rises, giving power loss high in the range instead of an idle misfire. A drifting sensor shifting the readings biases fuelling for the whole engine, which cannot produce a single hole code.
- An engine is experiencing detonation. Which of the following could be a cause for this condition?
- EGR valve pintle jammed widely opened
- ICM spark advance retarded quite late
- RON octane number graded plainly high
- ECT sensor output biased falsely cold
Correct answer: ECT sensor output biased falsely cold
The key is ECT sensor output biased falsely cold. When the coolant temperature signal reads colder than the engine really is, the control module keeps applying its cold engine fuel and spark strategy long after warm up, so the charge is mistimed for the actual chamber temperature and the mixture burns violently instead of smoothly. EGR valve pintle jammed widely opened does the opposite, since recirculated inert gas lowers peak combustion temperature and suppresses knock. ICM spark advance retarded quite late also suppresses knock, because retarding spark is the standard cure for it. RON octane number graded plainly high raises the fuel's resistance to autoignition, so it cannot bring detonation on.
- When checking for an intermittent stalling issue, which of the following is the LEAST likely to be checked first?
- Fuel filler cap seal integrity
- Idle air control valve plunger
- Crank sensor connector pin fit
- Throttle body bore carbon film
Correct answer: Fuel filler cap seal integrity
The key is Fuel filler cap seal integrity. A poor cap seal shows up as an evaporative emission leak, not as an engine that dies without warning, so it sits at the bottom of any stalling worklist. Idle air control valve plunger travel governs how much air bypasses a closed throttle, and a sticking plunger drops the engine below its idle floor. Crank sensor connector pin fit matters because a momentary loss of that signal cuts spark and injection instantly, which is the classic intermittent stall. Throttle body bore carbon film narrows the same bypass path and lets idle collapse as soon as load is applied.
- Which condition can cause an engine's operating temperature to rise excessively only at high speeds?
- A defective coolant filler cap
- A partly blocked radiator core
- A stalled electric fan circuit
- A depleted crankcase oil level
Correct answer: A partly blocked radiator core
The key is A partly blocked radiator core. Heat rejection has to climb with road load, and a core whose tubes or fins are partly plugged can still cope with the modest heat of town driving while falling behind once the engine is working hard, so the gauge climbs only at speed. A defective coolant filler cap lowers the boiling point of the system and lets it overheat in any condition, not just at speed. A stalled electric fan circuit produces the opposite pattern, since the fan matters at a standstill and ram air takes over once the vehicle is moving. A depleted crankcase oil level raises friction heat everywhere and is not speed-selective.
- A technician finds oil in the coolant of an engine. What is the MOST likely cause?
- A clogged filter element
- A collapsed coolant hose
- A perforated head gasket
- A fractured piston skirt
Correct answer: A perforated head gasket
The key is A perforated head gasket. The gasket is the only part sealing pressurized oil galleries from coolant jackets across the deck, so once it is breached the two fluids share a path and oil shows up in the coolant. A clogged filter element restricts oil flow and opens the bypass valve, but it cannot move oil into a separate circuit. A collapsed coolant hose starves the pump inlet and causes overheating with no route for oil to enter. A fractured piston skirt lets oil and combustion gas mix inside the cylinder, which fouls plugs and raises consumption rather than contaminating the coolant.
- Technician A says that a knock sensor is used to detect cylinder knocking and adjust ignition timing to prevent it. Technician B says that a knock sensor can adjust fuel pressure to prevent knocking. Who is correct?
- Technician B only
- Both Technician A and Technician B
- Neither Technician A nor Technician B
- Technician A only
Correct answer: Technician A only
The key is Technician A only. Technician A is right: the knock sensor is a piezoelectric element tuned to the frequency of abnormal combustion, and the control module answers its signal by retarding spark until the rattle stops. Technician B is wrong: fuel pressure is set by the pump and the regulator or by a pressure sensor feeding the module, and no knock strategy commands it, so the knock sensor has no authority there. That makes Both Technician A and Technician B too generous, Technician B only plainly false, and Neither Technician A nor Technician B wrong because the first claim stands.
- When a turbocharged engine is producing less boost than expected, which of the following should be checked FIRST?
- The wastegate actuator control system
- The exhaust manifold pressure readout
- The intake plenum gasket displacement
- The measured engine compression ratio
Correct answer: The wastegate actuator control system
The key is The wastegate actuator control system. Boost level is set by how much exhaust the wastegate spills, so a stuck-open flapper, a split actuator can, a disconnected rod or a leaking control hose all bleed boost away, and every one of those is quick to test at the front of the job. The exhaust manifold pressure readout needs a drilled port and a gauge, which is a late-stage measurement rather than a first look. The intake plenum gasket displacement would give a vacuum leak and a lean code before it noticeably lowered indicated boost. The measured engine compression ratio is a fixed design figure and cannot change to explain a sudden shortfall.
- In a diesel engine system, what is the main function of glow plugs?
- To purge the exhaust soot for clean filters
- To warm the cylinder charge for cold starts
- To govern the fuel delivery for heavy loads
- To ignite the intake vapor for early events
Correct answer: To warm the cylinder charge for cold starts
The key is To warm the cylinder charge for cold starts. A compression ignition engine has no spark, so it depends on the heat of compression alone, and when the block is cold that heat leaks into the metal faster than it builds, so the glow element raises chamber temperature far enough for the injected spray to light. To purge the exhaust soot for clean filters describes filter regeneration, which is handled by late injection or a dosing burner downstream. To govern the fuel delivery for heavy loads is the work of the pump and injectors, since the element carries current and no fuel. To ignite the intake vapor for early events misstates the cycle, because fuel is not in the chamber until the injector fires near the top of compression.
- What could cause an engine with electronic fuel injection to flood during startup?
- Delivery rail pressure inadequate
- Coolant sensor falsely overheated
- Injectors jammed permanently open
- Crankshaft position signal absent
Correct answer: Injectors jammed permanently open
The key is Injectors jammed permanently open. An injector held off its seat dumps fuel whenever the rail is charged, so the chamber wets down long before the engine has enough speed to burn it, which is exactly the flooded no-start picture. Delivery rail pressure inadequate produces the opposite complaint, a lean crank that fires and dies. Coolant sensor falsely overheated makes the module shorten pulse width because it believes the engine is already warm, so the mixture goes lean rather than rich. Crankshaft position signal absent stops injection entirely, since the module has no reference to time a pulse against, and an engine that receives no fuel cannot flood.
- When a vehicle with an overhead cam engine has a timing belt failure, which of the following is MOST likely to occur?
- The engine will forfeit its charge regulation.
- The engine will obstruct its exhaust passages.
- The engine will interrupt its oil circulation.
- The engine will lose its cylinder compression.
Correct answer: The engine will lose its cylinder compression.
The key is The engine will lose its cylinder compression. The belt is the only link driving the camshaft, so once it parts the valves stop moving and stand wherever they were left; cylinders whose valves are off their seats can no longer seal, and cranking produces little or no reading. The engine will forfeit its charge regulation is wrong on most designs because the alternator is turned by the accessory drive belt, a separate item. The engine will obstruct its exhaust passages is wrong because nothing about a parted belt blocks the exhaust tract. The engine will interrupt its oil circulation is wrong because the oil pump is driven from the crankshaft, which keeps turning.
- A technician has determined that a vehicle's multiport fuel injection system is not delivering fuel to one of the cylinders. What should be checked FIRST to diagnose this problem?
- ECU drive pulse at the injector
- EFI pump pressure at the outlet
- RON octane sample at the sender
- HEGO voltage trace at the probe
Correct answer: ECU drive pulse at the injector
The key is ECU drive pulse at the injector. On a multiport system each hole has its own driver, so a single dead hole splits cleanly into an electrical fault or a mechanical one, and a noid light or scope at the connector settles that in a minute before anything is dismantled. EFI pump pressure at the outlet is common to the whole rail and cannot starve one hole while feeding the rest. RON octane sample at the sender is also shared by every hole, so poor fuel would upset all of them. HEGO voltage trace at the probe reports the averaged result of combustion downstream and identifies nothing about which driver failed.
- When an engine misfires, Technician A says it could be due to a faulty mass airflow sensor (MAF). Technician B says it could be because of a defective Variable Valve Timing (VVT) solenoid. Who is correct?
- Technician A only
- Both Technician A and Technician B
- Technician B only
- Neither Technician A nor Technician B
Correct answer: Both Technician A and Technician B
The key is Both Technician A and Technician B. Technician A is right: a contaminated or drifting mass airflow signal makes the module calculate the wrong charge mass, and the resulting mixture error can be far enough off to stop a cylinder lighting reliably. Technician B is right as well: a stuck or slow variable valve timing solenoid parks the cam away from its commanded angle, which spoils cylinder filling and exhaust scavenging and shows up as a misfire, usually worst at idle or low load. Since both claims describe real misfire mechanisms, Technician A only and Technician B only each leave a genuine cause unaccounted for, and Neither Technician A nor Technician B rejects both.
- A vehicle with an automatic transmission experiences no movement in any gear. What is the FIRST thing a technician should check?
- Shift codes on the datalink
- Line pressure on the gauges
- Fluid level on the dipstick
- Filter debris on the magnet
Correct answer: Fluid level on the dipstick
The key is Fluid level on the dipstick. A hydraulic unit makes no torque without fluid to charge the pump, and a level low enough to let the pickup draw air kills drive in every range at once, so it is the cheapest and fastest check before anything is dismantled. Shift codes on the datalink may be worth reading afterwards, but a starved pump often sets nothing at all. Line pressure on the gauges is a useful second test that means nothing until the level has been confirmed. Filter debris on the magnet is seen only once the pan is dropped, which is a teardown step rather than a first check.
- During a road test, a technician notes that an automatic transmission slips momentarily when shifting into overdrive. Which of the following is the MOST likely cause?
- Overdrive lockup clutch kept open
- Overdrive planet gears badly worn
- Overdrive servo fluid overly aged
- Overdrive band adjusted too loose
Correct answer: Overdrive band adjusted too loose
The key is Overdrive band adjusted too loose. The band has to clamp its drum the instant the servo strokes, and slack in the adjustment lengthens that stroke so the drum turns briefly under the band before it grips, which the driver feels as a momentary flare on that one shift. Overdrive lockup clutch kept open costs efficiency and lets converter slip persist across every range, not just at this change. Overdrive planet gears badly worn produce noise and eventual breakage, since a gearset transmits torque through meshed teeth and cannot slip. Overdrive servo fluid overly aged would upset engagement quality generally rather than isolating the fault to one flare.
- When diagnosing an automatic transmission that shifts too early and too softly, the technician should FIRST look for which of the following conditions?
- Deficient hydraulic line pressure
- Stiffer accumulator piston spring
- Thickened varnish residue buildup
- Damaged shift solenoid harnesses
Correct answer: Deficient hydraulic line pressure
The key is Deficient hydraulic line pressure. Shift points and apply firmness both follow the pressure the pump and regulator hold, so when it falls the governor and throttle circuits reach their trip values sooner and the clutches take up gently, giving early and mushy changes together. Stiffer accumulator piston spring does the reverse, cushioning less and producing firm, late changes. Thickened varnish residue buildup sticks spool valves and gives erratic or delayed behavior rather than a consistent early and soft pattern. Damaged shift solenoid harnesses usually drop a range altogether or set a code instead of moving the whole schedule uniformly downward.
- What would be the likely result of a restricted transmission fluid filter?
- Fast engagement plus a firm shift
- Slow engagement plus a noisy pump
- Harsh engagement plus a cool sump
- Rapid engagement plus a quiet hum
Correct answer: Slow engagement plus a noisy pump
The key is Slow engagement plus a noisy pump. A blocked filter throttles the pump inlet, so the pump cavitates and whines while the circuit downstream is slow to build the pressure that clutches and bands need, and the driver waits before drive takes up. Fast engagement plus a firm shift describes healthy or high pressure, the opposite of a starved inlet. Harsh engagement plus a cool sump is wrong twice over, because starvation softens rather than sharpens apply and the extra slip drives sump temperature up. Rapid engagement plus a quiet hum simply describes a healthy transmission and names no fault at all.
- What component in an automatic transmission provides the means to drive the vehicle in reverse?
- The reverse planet gearsets
- The reverse torque coupling
- The reverse clutch assembly
- The reverse shift solenoids
Correct answer: The reverse clutch assembly
The key is The reverse clutch assembly. Backing up needs one more holding member applied than any forward range uses, and it is that clutch pack, splined to the drum the gearset reacts against, whose apply reverses output rotation. The reverse planet gearsets are meshed members that change ratio and direction only when a clutch or band holds one of them, so on their own they select nothing. The reverse torque coupling multiplies and transmits torque in whatever direction the gearset has already chosen. The reverse shift solenoids merely route fluid to the holding members on command and hold nothing themselves.
- Technician A says that a slipping torque converter can cause a decrease in fuel efficiency. Technician B says that a malfunctioning torque converter can lead to increased transmission temperatures. Who is correct?
- Technician A only
- Technician B only
- Neither Technician A nor Technician B
- Both Technician A and Technician B
Correct answer: Both Technician A and Technician B
The key is Both Technician A and Technician B. Technician A is right: a converter that slips instead of coupling lets the impeller outrun the turbine, so part of the crankshaft output never reaches the gearset and the driver has to hold more throttle for the same road speed, which shows at the pump. Technician B is right as well: that same slip is a shearing action in the fluid, and the energy lost there leaves as heat, driving sump temperature up and cooking the fluid. Because the two claims describe the same fault seen from opposite ends, Technician A only and Technician B only are each incomplete, and Neither Technician A nor Technician B denies both.
- Which of the following conditions would MOST likely be caused by a defective transmission pressure control solenoid?
- Harsh unpredictable gear changes
- Brief neutral coasting intervals
- Missing reverse range engagement
- Regular converter clutch shudder
Correct answer: Harsh unpredictable gear changes
The key is Harsh unpredictable gear changes. That solenoid meters the pressure the regulator holds, so when it drifts or sticks the apply pressure is wrong by a varying amount and the clutches grab too hard on one change and too gently on the next. Brief neutral coasting intervals point to a broken apply circuit or a failed holding member rather than to a pressure that is merely mistrimmed. Missing reverse range engagement traces to that range's own circuit or member, which a general pressure fault would not single out. Regular converter clutch shudder comes from the lockup apply and its own control, not from the shift quality fault the question describes.
- A customer complains of a whirring sound that changes pitch with vehicle speed in all gears, including neutral. What is the MOST likely source of this noise?
- Torque converter stator hub
- Input shaft support bearing
- Internal pump drive bushing
- Reverse idler thrust washer
Correct answer: Input shaft support bearing
The key is Input shaft support bearing. A member that turns whenever the vehicle is moving, whatever range is selected and even with none selected, has to sit ahead of the gearsets on the shaft that is always in motion, and a dry or brinelled bearing there whirrs and rises in pitch as it speeds up. Torque converter stator hub trouble follows engine speed, so it would be heard standing still with the engine revved. Internal pump drive bushing wear is audible at idle before the vehicle has moved at all. Reverse idler thrust washer damage can only be heard in the one range that turns that member.
- If an automatic transmission experiences delayed engagement only when cold, which of the following is the MOST likely cause?
- Slightly reduced sump oil volume
- Faulty fluid temp sensor circuit
- Sticky control body spool valves
- Heat driven viscosity shear loss
Correct answer: Sticky control body spool valves
The key is Sticky control body spool valves. Varnish and tight bore clearances bind a spool hardest when everything is cold and the fluid is thick, so apply pressure reaches the clutch late; once the castings warm and expand the spool frees off and engagement returns to normal, which is exactly the cold-only pattern. Slightly reduced sump oil volume would delay engagement whatever the temperature, and usually worst when hot and thin. Faulty fluid temp sensor circuit alters shift scheduling and converter lockup rather than the time taken to take up drive. Heat driven viscosity shear loss produces thin fluid and its symptoms appear when hot, the opposite way round.
- After rebuilding an automatic transmission, a technician notes that the transmission exhibits no forward movement, but reverse operates normally. What could be the cause of this condition?
- Forward converter pilot twisted
- Forward cooler pipework blocked
- Forward band assembly fractured
- Forward clutch plunger unseated
Correct answer: Forward clutch plunger unseated
The key is Forward clutch plunger unseated. Every forward range applies that one pack, while reverse gets its holding members elsewhere, so a plunger left cocked in its bore leaks its apply pressure away and gives no drive ahead while backing up is untouched, which is precisely the split described. Forward converter pilot twisted would stop drive in both directions, since everything passes through the coupling. Forward cooler pipework blocked overheats the unit and eventually damages it in all ranges rather than removing one direction. Forward band assembly fractured would be felt on the ranges that band serves, and would not leave every forward gear dead while reverse stayed normal.
- When a technician is unable to shift into any gear with the engine running, but can do so when the engine is off, what should be checked FIRST?
- Hydraulic clutch release circuit
- Friction disc facing measurement
- Gearshift linkage pin adjustment
- Flywheel pilot bushing clearance
Correct answer: Hydraulic clutch release circuit
The key is Hydraulic clutch release circuit. Gears go in freely with the engine stopped and refuse with it running, which says the driven member is still being turned, so the release side is not moving the pressure plate far enough; a low reservoir, air in the line or a passed master seal all do that and all are quick to check. Friction disc facing measurement needs the unit dismantled and would not be reached before the simple hydraulic tests. Gearshift linkage pin adjustment cannot be the fault because the same linkage selects every gear perfectly with the engine off. Flywheel pilot bushing clearance would give noise and drag rather than a clean loss of release.
- A vehicle with a manual transmission is difficult to shift into all gears. The MOST likely cause of this condition is:
- Extensively worn driven plates
- Aerated clutch hydraulic fluid
- Glazed synchronizer cone faces
- Misadjusted shift linkage rods
Correct answer: Aerated clutch hydraulic fluid
The key is Aerated clutch hydraulic fluid. Air compresses where fluid does not, so pedal travel is spent squeezing bubbles instead of stroking the release fork, the driven member keeps turning, and every gear is a fight to select. Extensively worn driven plates cause slip under power and a high biting point, not a release problem, so gears would still select. Glazed synchronizer cone faces bite badly only in the ratios they serve, which would spare at least one gear and reverse. Misadjusted shift linkage rods usually obstruct one gate or one plane of movement rather than making the whole gate pattern equally difficult.
- A customer complains of a grinding noise when shifting into reverse. The MOST likely cause is:
- A notched reverse blocker ring
- A leaking reverse gearbox seal
- A damaged reverse idler pinion
- A weakened reverse detent ball
Correct answer: A damaged reverse idler pinion
The key is A damaged reverse idler pinion. Backing up is usually taken through a sliding idler with straight cut teeth and no cone to match speeds, so chipped or burred teeth on that member clash as it slides into mesh and make the grinding the driver reports. A notched reverse blocker ring cannot be the fault on the great majority of designs, because that range has no synchronizer fitted to wear. A leaking reverse gearbox seal lowers the oil level and brings whine and general wear across every range rather than a noise confined to one selection. A weakened reverse detent ball lets the lever creep out of engagement without clashing teeth on the way in.
- Technician A says that a clicking noise from the front of the vehicle during tight turns can be caused by a failing CV joint. Technician B says that a failing wheel bearing can also cause a clicking noise during tight turns. Who is correct?
- Technician B only
- Both Technician A and Technician B
- Neither Technician A nor Technician B
- Technician A only
Correct answer: Technician A only
The key is Technician A only. Technician A is right: an outer constant velocity joint runs at its largest articulation angle on full lock, and worn ball tracks knock once per revolution there, which the driver hears as a rhythmic clicking that stops as the wheel is straightened. Technician B is wrong: a failing hub bearing growls or hums and its pitch follows road speed; cornering shifts the load and may change the volume, but it does not turn a hum into a click. That makes Both Technician A and Technician B too generous, Technician B only false, and Neither Technician A nor Technician B wrong because the first claim holds.
- What is the purpose of a pilot bearing in a manual transmission vehicle?
- To support the input shaft nose
- To align the friction plate hub
- To stop the crankshaft end play
- To speed the gear change action
Correct answer: To support the input shaft nose
The key is To support the input shaft nose. The gearbox shaft is held at its own end by the case, and its front tip is carried in a bearing pressed into the end of the crankshaft, which keeps the shaft concentric with engine rotation so the driven plate runs true. To align the friction plate hub describes what an alignment tool does during assembly, and the tool is withdrawn before the engine ever runs. To stop the crankshaft end play is the job of the thrust bearing in the block. To speed the gear change action belongs to the synchronizers, which match shaft speeds inside the gearbox.
- Which of the following could be a cause for a manual transmission not maintaining in a gear?
- Deformed rear crossmember bracket
- Damaged synchronizer sleeve teeth
- Overfilled gearbox lubricant sump
- Perforated release slave cylinder
Correct answer: Damaged synchronizer sleeve teeth
The key is Damaged synchronizer sleeve teeth. The sliding sleeve holds a ratio by the back-tapered dog teeth it engages, and once those chamfers are rounded or chipped the load between them develops an axial component that pushes the sleeve out of mesh, so the lever jumps back toward neutral under power. Deformed rear crossmember bracket alters driveline angle and can add vibration, but it does not release an engaged sleeve. Overfilled gearbox lubricant sump causes aeration, foaming and leaks rather than loss of engagement. Perforated release slave cylinder makes gears hard to select in the first place, which is a different complaint from failing to hold one once selected.
- A rear-wheel-drive vehicle has a vibration that increases with speed. Technician A says this could be due to a bent drive shaft. Technician B says that it could be caused by a damaged differential pinion gear. Who is correct?
- Technician B only
- Both Technician A and Technician B
- Technician A only
- Neither Technician A nor Technician B
Correct answer: Technician A only
The key is Technician A only. Technician A is right: a bent shaft is out of balance about its own axis, and the force it throws grows with the square of rotational speed, so the shake is mild at low speed and severe as the vehicle speeds up. Technician B is wrong: damaged pinion teeth are a meshing fault, and a bad mesh announces itself as a whine, howl or clunk on drive and overrun rather than as a smooth rising vibration. So Both Technician A and Technician B claims too much, Technician B only is false, and Neither Technician A nor Technician B ignores a sound first diagnosis.
- What is the primary function of the differential in a vehicle's drive train?
- To divide engine effort between axles
- To raise the driveshaft torque figure
- To connect the driven wheels together
- To permit unequal driven wheel speeds
Correct answer: To permit unequal driven wheel speeds
The key is To permit unequal driven wheel speeds. On any curve the outer tire traces a longer arc than the inner one in the same time, so unless the two driven wheels can turn at different rates one of them must scrub, and the gearset exists to let them differ while both are still driven. To divide engine effort between axles describes a transfer case or center unit fitted only to vehicles driving both ends. To raise the driveshaft torque figure is done by the final drive ratio and the gearbox ratios rather than by the side gears. To connect the driven wheels together is what a spool or a locked unit does, and it is the opposite of the purpose of the gearset.
- When diagnosing a high-pitched whine that is present only when the clutch is engaged, what should be suspected?
- Worn crankshaft pilot bearing
- Seized clutch release bearing
- Pitted mainshaft rear bearing
- Dry driveshaft center bearing
Correct answer: Worn crankshaft pilot bearing
The key is Worn crankshaft pilot bearing. As keyed, the complaint is tied to the state of the clutch rather than to road speed, and the only bearing that sits directly between the crankshaft and the gearbox input shaft is the pilot, so a dry or brinelled one is the member blamed here. Seized clutch release bearing is not it, because that bearing is loaded and turning only while the pedal is being held down, which is the opposite pedal position. Pitted mainshaft rear bearing would produce a noise that tracks road speed and would still be heard on the overrun with the pedal down. Dry driveshaft center bearing sits outside the housing entirely and likewise follows road speed, not clutch state.
- A four-wheel-drive vehicle's front wheels do not engage when the transfer case is set to the 4WD mode. The MOST likely cause is:
- A fractured front axle half shaft
- A dead front shift actuator motor
- A chipped front pinion gear tooth
- A slack front propshaft yoke bolt
Correct answer: A dead front shift actuator motor
The key is A dead front shift actuator motor. On an electronically selected system the switch only asks for the range; a motor has to drive the sleeve across to couple the front output, and if that motor or its position encoder is dead the sleeve never moves, so nothing is driven forward however the switch is set. A fractured front axle half shaft would leave one wheel dead while the other still received drive through the differential. A chipped front pinion gear tooth makes noise and eventually breaks, but the mesh still transmits drive until it does. A slack front propshaft yoke bolt causes vibration and a clunk and is a safety concern, yet the shaft continues to turn the axle.
- When inspecting a drive axle, the technician finds metal flakes in the differential fluid. What is the MOST likely source of these flakes?
- Roughened outboard wheel races
- Perforated inboard shaft seals
- Fatigued carrier side bearings
- Expected crownwheel tooth wear
Correct answer: Fatigued carrier side bearings
The key is Fatigued carrier side bearings. Rolling-element fatigue lifts flakes of hardened steel out of the races as the surface spalls, and those bearings sit inside the housing bathed in the same oil that was drained, so their debris is what the technician is looking at. Roughened outboard wheel races are packed or sealed separately at the ends of the axle tubes and do not share that oil supply on most designs. Perforated inboard shaft seals let oil out and dirt in, but a rubber lip cannot shed steel flakes. Expected crownwheel tooth wear polishes and burnishes the tooth faces, producing a fine gray sludge on the magnet rather than visible bright flakes.
- What would be the most likely cause of an intermittent clunking noise from the front suspension when driving over bumps?
- Weeping steering rack seals
- Flattened rear coil springs
- Softened motor mount rubber
- Loosened swivel ball joints
Correct answer: Loosened swivel ball joints
The key is Loosened swivel ball joints. A worn joint has free play in its socket, so each time the wheel drops into a hollow and is loaded again the stud takes up that slack against the housing with a metallic knock, which is why the noise comes and goes with the road surface. Weeping steering rack seals show as fluid loss and heavy steering, with no impact noise. Flattened rear coil springs sag and harden the ride at the wrong end of the vehicle. Softened motor mount rubber thumps when torque reverses on gear changes rather than when a wheel meets a bump.
- When performing an alignment, you notice that the front wheels are tilted outward at the top. This condition is known as:
- Positive camber angle
- Negative camber angle
- Positive caster angle
- Negative caster angle
Correct answer: Positive camber angle
The key is Positive camber angle. Camber is the tilt of the wheel plane away from vertical seen from directly in front of the vehicle, and the sign convention calls it positive when the top of the wheel leans away from the centreline, which is exactly the outward lean described. Negative camber angle is the same measurement with the top leaning inward toward the vehicle, the reverse of what was observed. Positive caster angle is not a lean at all but the rearward tilt of the steering axis seen from the side, which is why it governs straight-line stability and self-return rather than tire attitude. Negative caster angle is that same steering axis tilted forward, and it too is invisible from directly in front.
- During a test drive, a customer's vehicle exhibits a steering wheel shake at highway speeds. What is the MOST likely cause of this issue?
- Misaligned front toe adjustment
- Unbalanced tire assembly masses
- Worn outboard steering linkages
- Depleted power assist reservoir
Correct answer: Unbalanced tire assembly masses
The key is Unbalanced tire assembly masses. A heavy spot rotating off center throws a force that grows with the square of speed, so it is unnoticed around town and reaches the steering as a rhythmic shake once the wheel speed rises to motorway rates. Misaligned front toe adjustment scrubs the tread and pulls the vehicle to one side, producing wear and a lead rather than a shake. Worn outboard steering linkages give vague response, wander and knocking over bumps, and they let a vibration through rather than creating one. Depleted power assist reservoir makes the wheel heavy at parking speeds and may make the pump whine, which is a completely different complaint.
- Technician A states that a weak power steering pump can cause hard steering at low speeds. Technician B says that a worn steering rack can cause hard steering at all speeds. Who is correct?
- Technician A only
- Technician B only
- Both Technician A and Technician B
- Neither Technician A nor Technician B
Correct answer: Both Technician A and Technician B
The key is Both Technician A and Technician B. Technician A is right: assist demand is greatest when the tires are turned against a stationary or nearly stationary contact patch, and a pump that cannot make its rated flow at idle speed leaves the driver doing that work, so the effort is worst parking and eases as speed and pump output rise. Technician B is right as well: a rack worn in its bore or on its piston seal leaks internally, and that leak bleeds assist away at every speed rather than only at one end of the range. Since each claim stands on its own, Technician A only and Technician B only both discard a valid point, and Neither Technician A nor Technician B discards both.
- What could be the cause of a vehicle pulling to one side when braking?
- Unequal tire inflation on one side
- Loose steering linkage on one side
- Sticking brake caliper on one side
- Excessive camber angle on one side
Correct answer: Sticking brake caliper on one side
Sticking brake caliper on one side is the cause: a caliper that will not release clamps that wheel harder than its partner, so the vehicle veers toward the dragging corner the moment the pedal is applied. Unequal tire inflation on one side alters rolling radius and gives a steady pull that is present whether or not the brakes are used. Loose steering linkage on one side produces wander and free play, never a directional pull tied to pedal pressure. Excessive camber angle on one side skews tire wear and causes a constant drift rather than a braking-only pull.
- A technician notices uneven tire wear on the outer edges of the front tires. This is MOST likely due to:
- Chronic front tire underinflation
- Maladjusted wheel bearing preload
- Uncorrected negative camber angle
- Excessive positive toe adjustment
Correct answer: Excessive positive toe adjustment
Excessive positive toe adjustment is the cause: with the front wheels aimed inward of straight, each tire is dragged sideways as the car rolls forward and scuffs its outer shoulder. Chronic front tire underinflation loads both shoulders together, so the inner edges would be worn as well. Maladjusted wheel bearing preload lets the wheel wobble and leaves cupped or scalloped patches instead of a clean outer-edge band. Uncorrected negative camber angle tips the top of the tire inward and wears the inner edge, the opposite of what was found.
- A vehicle equipped with a MacPherson strut suspension system is experiencing a squeaking noise at low speeds and during turning maneuvers. The MOST likely cause is:
- A worn upper mount bearing
- A dry jounce bumper sleeve
- A broken front coil spring
- A torn control arm bushing
Correct answer: A worn upper mount bearing
A worn upper mount bearing is the cause: on a MacPherson strut the upper mount carries a bearing that lets the whole strut rotate with the steering, and dry or brinelled races chirp each time the wheel is turned at low speed. A dry jounce bumper sleeve contacts only on hard compression, so it stays silent through a smooth parking-lot turn. A broken front coil spring announces itself with a clunk and a lost ride height rather than a squeak. A torn control arm bushing knocks over bumps and does not bind through the steering arc.
- What would cause a steering wheel to be off-center when driving straight?
- A worn rear hub bearing
- A bent tie rod assembly
- A seized brake pad clip
- A dry upper strut mount
Correct answer: A bent tie rod assembly
A bent tie rod assembly is the cause: bending the rod changes the effective length of one steering link, so the wheels only track straight ahead once the rim is held away from its centered position. A worn rear hub bearing rumbles and lets the rear wheel wobble without shifting where the rim rests. A seized brake pad clip drags one pad and overheats a rotor, yet the toe setting is untouched. A dry upper strut mount squeaks and slows steering return, while the rim still settles at its original center.
- If a vehicle has excessive steering wheel play, what should be inspected FIRST?
- Power pump drive belt slack
- Gear box worm shaft preload
- Tie rod end joint condition
- Wheel bearing hub side play
Correct answer: Tie rod end joint condition
Tie rod end joint condition is what to inspect first: worn ball sockets in the tie rod ends let the road wheel move before the linkage takes up, which is precisely the free travel a driver feels at the rim. Power pump drive belt slack changes assist effort and pump noise, not mechanical free travel. Gear box worm shaft preload is adjusted only once linkage wear has been ruled out, because a worn joint corrupts any lash reading taken first. Wheel bearing hub side play shows up as wheel wobble and irregular tire wear rather than free travel at the rim.
- When checking a vehicle's suspension, the technician finds that the rear of the vehicle is lower than the front. This is MOST likely due to:
- Weak rear shock valves
- Bent rear spring seats
- Rusted rear track bars
- Worn rear leaf springs
Correct answer: Worn rear leaf springs
Worn rear leaf springs is the cause, since a leaf pack loses its arch as the steel takes a set, so the back of the vehicle settles while the front keeps its original height. Weak rear shock valves control body motion but carry no static load, so ride height is unchanged by them. Bent rear spring seats belong to a coil sprung axle and would drop one corner abruptly rather than let the whole rear sag. Rusted rear track bars locate the axle sideways and have no part in holding the body up.
- Which component is MOST likely to cause a rapid 'clunk' or 'knock' sound when quickly turning the steering wheel back and forth at a standstill?
- Loose rack mounting bushings
- Dry steering column bearings
- Aerated power steering fluid
- Perished trailing arm bushes
Correct answer: Loose rack mounting bushings
Loose rack mounting bushings is the cause: when the rack housing can shift in its mounts, every reversal of the wheel lets the housing slam against the bushing and produces the rapid knock heard while parked. Dry steering column bearings creak or squeak as the shaft turns and give no metallic knock. Aerated power steering fluid makes a whine or groan that rises with steering effort rather than a knock. Perished trailing arm bushes sit at the rear of the vehicle and speak over bumps, not during a stationary steering reversal.
- When diagnosing a vehicle with ABS, a technician finds that one wheel consistently locks up during heavy braking. What could be the primary cause of this condition?
- A grounded ABS pump motor relay
- A failed ABS wheel speed sensor
- A leaking ABS brake fluid union
- A cracked ABS wheel hub carrier
Correct answer: A failed ABS wheel speed sensor
A failed ABS wheel speed sensor is the primary cause, because with no usable signal from that corner the controller cannot see the wheel decelerating, so it never releases pressure there and that one wheel locks while the rest are managed normally. A grounded ABS pump motor relay takes the whole system offline, leaving all four wheels unregulated instead of one. A leaking ABS brake fluid union starves that corner of pressure, so the wheel would brake weakly rather than lock. A cracked ABS wheel hub carrier is a structural fault that never reaches the controller's wheel speed data.
- A soft brake pedal is noted during initial vehicle start-up, but firms up after the engine is running. The MOST likely cause of this condition is:
- Brake line trapped air pockets
- Brake master cylinder lip seal
- Brake booster vacuum hose leak
- Brake ABS pump discharge valve
Correct answer: Brake booster vacuum hose leak
Brake booster vacuum hose leak is the keyed cause: the booster is the only part of the system whose behavior is tied to whether the engine is turning, so a pedal that changes character once the engine runs points at the vacuum supply to the booster. Brake line trapped air pockets give a spongy pedal that feels the same with the engine stopped or running. Brake master cylinder lip seal wear lets the pedal creep toward the floor under steady foot pressure rather than change with engine state. Brake ABS pump discharge valve trouble shows up as noisy stops and stored codes, not as a start-up pedal change.
- If a vehicle's brakes drag and do not release immediately when the pedal is released, the FIRST component to inspect should be the:
- Caliper hardware for corrosion damage
- Wheel cylinders for hydraulic seepage
- Pedal linkage for restricted movement
- Master cylinder for retained pressure
Correct answer: Master cylinder for retained pressure
Master cylinder for retained pressure is the first component to inspect: if the piston cannot return far enough to uncover the compensating port, pressure stays trapped in the lines and every brake keeps applying after the driver lifts off. Caliper hardware for corrosion damage explains one dragging corner, not a system that hangs on everywhere. Wheel cylinders for hydraulic seepage points to a fluid leak, which bleeds pressure away instead of holding it. Pedal linkage for restricted movement is worth checking once the hydraulic side has been cleared, but it is not where the inspection starts.
- A vehicle exhibits a squealing noise from the brakes at low speeds. The noise stops when the brake pedal is applied. The MOST likely cause is:
- Worn brake wear indicator tabs
- Glazed brake pad contact faces
- Loose brake caliper slide pins
- Scored brake rotor swept areas
Correct answer: Worn brake wear indicator tabs
Worn brake wear indicator tabs is the cause: the steel tab reaches the disc once friction material is nearly used up and sings as the wheel turns, then goes quiet the moment pedal pressure clamps the pad flat against the rotor. Glazed brake pad contact faces squeal while the pedal is pressed, the reverse of the pattern described. Loose brake caliper slide pins rattle and clunk over bumps rather than sing steadily at low speed. Scored brake rotor swept areas grind during application and do not fall silent when the brakes are used.
- During a test drive, a pulsation is felt in the brake pedal when the brakes are applied. This symptom is MOST likely caused by:
- Sticking brake caliper pins
- Warped brake rotor surfaces
- Leaking brake booster valve
- Uneven brake shoe adjusters
Correct answer: Warped brake rotor surfaces
Warped brake rotor surfaces is the cause: thickness variation in the disc pushes the pad and piston back and forth once per revolution, and that motion travels up the fluid column into the pedal on every stop. Sticking brake caliper pins drag the pad against the disc and give heat, pull and fade rather than a cyclic pedal movement. Leaking brake booster valve trouble changes assist, so the pedal feels hard rather than pulsing. Uneven brake shoe adjusters leave a low pedal and a rear pull at the drums, with no once per revolution pulse.
- A customer complains that their vehicle pulls to the left when the brakes are applied. The technician should FIRST inspect the:
- Left-side cylinders for leaking
- Front-axle alignment for camber
- Right-hand caliper for sticking
- Rear-wheel pressure for balance
Correct answer: Right-hand caliper for sticking
Right-hand caliper for sticking is what to inspect first: a piston stuck in its bore on the right cannot clamp its rotor, so the left brake does nearly all the work and the vehicle noses to the left as soon as the pedal goes down. Left-side cylinders for leaking would weaken the left side instead, sending the vehicle the other way. Front-axle alignment for camber gives a steady drift that is present whether or not the brakes are used. Rear-wheel pressure for balance changes ride and rolling radius but does not create a braking-only pull.
- A vehicle's rear disc brakes have excessive dust on one side compared to the other. The technician should suspect:
- A collapsed rubber hose on the dustier wheel
- A binding parking cable on the noisier wheel
- A hardened friction pad on the dirtier wheel
- A frozen caliper piston on the cleaner wheel
Correct answer: A frozen caliper piston on the cleaner wheel
A frozen caliper piston on the cleaner wheel is what to suspect, because a piston that cannot move leaves its pad barely touching the disc, so that wheel makes almost no friction dust while its partner does the work and collects the rest. A collapsed rubber hose on the dustier wheel would starve the side that is already dusty, which is the reverse of the pattern found. A binding parking cable on the noisier wheel adds friction where the noise is rather than explaining an uneven dust split. A hardened friction pad on the dirtier wheel would shed less material there, so that side would be the cleaner one.
- What is the MOST likely cause of a brake warning light that illuminates during sharp turns and then turns off soon after?
- Low brake fluid volume in the master cylinder reservoir
- Chafed brake lamp harness in the dashboard fuse holders
- Faulty brake speed sensors in the rear wheel assemblies
- Sticky brake lever switch in the parking cable brackets
Correct answer: Low brake fluid volume in the master cylinder reservoir
Low brake fluid volume in the master cylinder reservoir is the most likely cause: with the level sitting close to the float, cornering slings the fluid to one end of the reservoir, the switch closes for a moment, and the lamp clears once the fluid settles back. Chafed brake lamp harness in the dashboard fuse holders would illuminate at random times with no link to cornering. Faulty brake speed sensors in the rear wheel assemblies set an antilock lamp and a stored code instead of a brief brake warning. Sticky brake lever switch in the parking cable brackets can only act when the lever itself moves, which it does not during a turn.
- Excessive pedal effort is required to stop the vehicle, but the braking performance is adequate. This condition is MOST likely caused by:
- A severely restricted brake circuit
- A defective brake booster diaphragm
- A vitrified brake friction material
- A misadjusted brake parking linkage
Correct answer: A defective brake booster diaphragm
A defective brake booster diaphragm is the cause: with the assist gone the driver supplies the whole clamping force by foot, so effort climbs steeply while the hydraulic system still delivers its normal stopping power. A severely restricted brake circuit would cut the pressure reaching one wheel and degrade stopping performance, which the customer reports as fine. A vitrified brake friction material lowers the coefficient of friction, so the vehicle would stop poorly rather than simply demand a hard push. A misadjusted brake parking linkage drags the rear shoes and produces heat and pull instead of high pedal effort.
- After a complete brake system service, the ABS light remains illuminated. The FIRST step in diagnosing this issue is to:
- Bleed the ABS circuit for air
- Reset the ABS memory for test
- Scan the ABS module for codes
- Check the ABS sensor for rust
Correct answer: Scan the ABS module for codes
Scan the ABS module for codes is the first diagnostic step: the stored fault names the circuit the module objected to, and every later test is chosen from it. Bleed the ABS circuit for air chases a pedal complaint nobody reported and clears no fault memory. Reset the ABS memory for test throws away the one piece of evidence the module has already recorded. Check the ABS sensor for rust is a targeted inspection that should follow a code pointing at that wheel rather than come before any code has been read.
- A vehicle's headlights dim when the RPMs drop at idle. The MOST likely cause of this is:
- A discharged battery storage element
- A corroded positive terminal fitting
- A resistive chassis ground connector
- A degraded alternator output voltage
Correct answer: A degraded alternator output voltage
A degraded alternator output voltage is the most likely cause: the alternator turns slowest at idle, and a unit whose output has fallen off can no longer hold system voltage up, so the lamps dim exactly as engine speed falls away. A discharged battery storage element weakens cranking but is masked once the charging system carries the load. A corroded positive terminal fitting produces a constant loss rather than one that tracks engine speed. A resistive chassis ground connector dims lamps whenever a load is switched on, not specifically as revs fall.
- A technician finds that the OBD II system is not communicating with the scan tool. The first thing to check should be:
- The OBD II system supply fuse
- The OBD DLC pin bus terminals
- The OBD PCM system data lines
- The OBD USB tool driver setup
Correct answer: The OBD II system supply fuse
The OBD II system supply fuse is the first thing to check: no scan tool can talk to a network whose power feed is open, and a blown fuse takes seconds to verify before anything is disassembled. The OBD DLC pin bus terminals matter only once power at the connector has been confirmed present. The OBD PCM system data lines sit further downstream and are examined after the connector itself proves sound. The OBD USB tool driver setup is worth revisiting only when the same tool also fails on a known-good vehicle.
- A vehicle exhibits a slow engine crank and the battery is known to be good. Which of the following could be the cause?
- Shorted copper in the armature laminations
- Elevated resistance in the starter circuit
- Broken continuity in the alternator wiring
- Excessive current in the battery terminals
Correct answer: Elevated resistance in the starter circuit
Elevated resistance in the starter circuit is the cause: corroded studs, loose clamps and tired cables all add voltage drop, so the motor receives less than it needs and turns slowly even though the battery itself tests good. Shorted copper in the armature laminations draws enormous current and normally shows as smoke or a tripped feed rather than a steady slow crank. Broken continuity in the alternator wiring stops the battery being replenished but does nothing while the starter is turning. Excessive current in the battery terminals restates a symptom instead of naming a fault that would slow cranking.
- When performing a voltage drop test on the ground side of a circuit, a reading of 0.4 volts is obtained. This indicates:
- The reading shows acceptable ground integrity
- The reading shows doubtful ground measurement
- The reading shows excessive ground resistance
- The reading shows insufficient ground voltage
Correct answer: The reading shows excessive ground resistance
The reading shows excessive ground resistance is what four tenths of a volt on the ground side means: a sound return path drops well under a tenth of a volt, so the measured value is unwanted resistance between the load and the battery. The reading shows acceptable ground integrity would require a far smaller number than the one obtained. The reading shows doubtful ground measurement is wrong because a voltage drop test is by definition taken with the circuit energized and loaded. The reading shows insufficient ground voltage misreads the test, which measures loss along the return rather than the level of supply.
- A technician cannot get the engine to crank. After verifying the battery is fully charged and the starter is good, the next step should be to:
- Replace the ignition start switch
- Test the starter safety interlock
- Read the stored immobilizer codes
- Inspect the starter control relay
Correct answer: Inspect the starter control relay
Inspect the starter control relay is the next step: the relay sits between the crank request and the motor, so a burnt contact or an open coil stops cranking even when the battery and the starter have both been proven good. Replace the ignition start switch throws a part at the fault before anything has proven it defective. Test the starter safety interlock follows later, once the relay has been shown to receive its command. Read the stored immobilizer codes addresses a fuel and spark shutdown, which would still leave the engine free to crank.
- A vehicle's electric cooling fan runs constantly, even when the engine is cold. What is the MOST likely cause?
- A shorted cooling fan relay
- A faulty cooling fan sensor
- A corroded cooling fan fuse
- A weak cooling fan resistor
Correct answer: A shorted cooling fan relay
A shorted cooling fan relay is the most likely cause: contacts welded closed feed the motor straight from the supply, so the fan turns whenever the key is on and pays no attention to coolant temperature. A faulty cooling fan sensor normally leaves the fan off or brings it on late rather than powering it continuously. A corroded cooling fan fuse adds resistance in the supply and would slow or stop the fan instead of running it. A weak cooling fan resistor alters speed on a multi-speed system but cannot switch power on by itself.
- Which of the following is an indication of a charging system problem?
- The dash gauge steadies with the engine warming
- The battery light glows with the engine running
- The interior lamp dims with the engine starting
- The blower motor weakens with the engine idling
Correct answer: The battery light glows with the engine running
The battery light glows with the engine running is the indication of a charging system problem, because that lamp compares charging output against battery voltage and illuminates when the alternator stops carrying the load. The dash gauge steadies with the engine warming is what a healthy system does once output settles at the regulated value. The interior lamp dims with the engine starting is expected, since the starter draws heavily for a moment. The blower motor weakens with the engine idling reflects reduced output at low speed on a loaded system rather than a fault.
- A vehicle's starter cranks excessively slow when the interior blower motor is turned on. This MOST likely indicates:
- A distorted starter motor commutator
- A resistive charging circuit contact
- A weakened battery cranking capacity
- A steady electrical accessory demand
Correct answer: A weakened battery cranking capacity
A weakened battery cranking capacity is what this points to: adding the blower load pulls terminal voltage down further, and a battery that can no longer hold up under load leaves too little for the starter to work with. A distorted starter motor commutator would crank slowly whether the blower was switched on or not. A resistive charging circuit contact affects replenishment once the engine runs and plays no part in cranking. A steady electrical accessory demand is normal on every vehicle and merely exposes a battery that is already marginal.
- A customer complains that their vehicle's starter intermittently does not engage. A technician should FIRST check:
- The ignition switch tumbler plunger
- The starter solenoid contact plates
- The gearbox range selector position
- The battery cable clamp connections
Correct answer: The battery cable clamp connections
The battery cable clamp connections should be checked first: a clamp that is loose or green under the cover carries current one moment and not the next, which is precisely the intermittent no-crank described, and it costs nothing to inspect. The ignition switch tumbler plunger is a deeper mechanical repair to attempt before the simple connections have been cleared. The starter solenoid contact plates do burn over time, but reaching them means removing the starter ahead of far easier checks. The gearbox range selector position is worth a look only once power delivery has been proven sound.
- During an inspection, a technician discovers that the alternator's B+ terminal is heavily corroded. This condition could result in:
- Reduced battery charging current
- Elevated charging system voltage
- Greater charging stator amperage
- Cleaner charging ripple waveform
Correct answer: Reduced battery charging current
Reduced battery charging current is the result, since corrosion at the output stud puts resistance in series with everything the alternator feeds, so less current reaches the battery and it is never brought back to full charge. Elevated charging system voltage cannot occur at the battery when resistance has been added to that same path. Greater charging stator amperage would demand that the alternator push more through the very connection restricting it. Cleaner charging ripple waveform describes an improvement in diode output quality, which a corroded terminal has no way to produce.
- Which of the following symptoms would MOST likely be caused by a faulty ignition module?
- Engine fires but does not settle
- Engine cranks but does not start
- Engine runs but does not respond
- Engine rattles but does not quit
Correct answer: Engine cranks but does not start
Engine cranks but does not start is the symptom most likely produced by a faulty ignition module: with no switching signal the coil never fires, so the starter turns the engine over and nothing ignites. Engine fires but does not settle points at fuel delivery or idle control rather than a total loss of spark. Engine runs but does not respond describes a throttle or fuel metering complaint on an engine that is clearly sparking. Engine rattles but does not quit is detonation, which comes from timing, fuel quality or carbon rather than a dead module.
- When diagnosing an A/C system that is not cooling properly, the technician finds that the compressor clutch engages, but the low-side pressure is high and the high-side pressure is low. This could indicate:
- A flooded compressor charge
- A choked compressor orifice
- A defective compressor pump
- A leaky compressor manifold
Correct answer: A defective compressor pump
A defective compressor pump is what these readings point to: a compressor that can no longer build a pressure difference lets the two sides drift toward each other, which is exactly the high low-side and low high-side pattern measured with the clutch engaged. A flooded compressor charge lifts both readings together instead of collapsing the split between them. A choked compressor orifice traps pressure upstream and drives the high side well above normal. A leaky compressor manifold bleeds charge away and pulls both readings down rather than bringing them together.
- A vehicle's HVAC system emits a musty odor when the A/C is first turned on. The most likely cause of the odor is:
- Compacted debris in the cabin filter
- Surplus refrigerant in the high side
- Coolant leakage in the heater matrix
- Fungal growth in the evaporator case
Correct answer: Fungal growth in the evaporator case
Fungal growth in the evaporator case is the most likely source of the odor: the evaporator stays wet and dark between cycles, mold and mildew colonize the case, and the first rush of air carries their musty smell into the cabin. Compacted debris in the cabin filter smells dusty rather than musty and would not clear as the system runs. Surplus refrigerant in the high side spoils cooling and raises pressures without producing any smell. Coolant leakage in the heater matrix gives a sweet antifreeze odor and a filmed windscreen instead.
- The A/C system is not producing cold air, and the compressor is not engaging. A proper diagnostic step is to:
- Check the actual pressures with manifold gauges
- Refill the empty circuit with fresh refrigerant
- Bypass the pressure switch with temporary leads
- Replace the compressor clutch with new hardware
Correct answer: Check the actual pressures with manifold gauges
Check the actual pressures with manifold gauges is the sound diagnostic step: the gauge set reports charge state and system behavior before anything is opened, defeated or replaced. Refill the empty circuit with fresh refrigerant puts gas into a system whose leak has never been located. Bypass the pressure switch with temporary leads defeats a protection device that may well be doing its job correctly. Replace the compressor clutch with new hardware commits money to a part that no measurement has yet implicated.
- A technician finds that the A/C system's high-pressure cut-off switch has tripped. The FIRST thing they should check is:
- The reading of the system charge
- The function of the cooling fans
- The status of the condenser fins
- The condition of the liquid line
Correct answer: The function of the cooling fans
The function of the cooling fans is the first thing to check: the condenser sheds heat only while air moves through it, and at low road speed the fans supply all of that airflow, so a dead fan sends head pressure straight up to the cut-off point. The reading of the system charge does matter, but an overcharge is a far less common trigger than a stopped fan. The status of the condenser fins is worth examining afterwards, since blocked fins raise pressure gradually instead of tripping the switch. The condition of the liquid line points at a restriction, which normally shows as poor cooling before any high-pressure trip.
- During an A/C system performance test, the center vent temperature is higher than specifications with the system set to max cool. The system's refrigerant charge level should be:
- Restored with a refrigerant kit
- Approximated with a sight glass
- Weighed with a recovery machine
- Evaluated with a colored tracer
Correct answer: Weighed with a recovery machine
Weighed with a recovery machine is how the charge level should be established: recovering the charge and measuring what comes out is the only method that yields an actual quantity to compare against specification. Approximated with a sight glass is unreliable on modern systems, and many vehicles have no sight glass fitted at all. Restored with a refrigerant kit adds gas without ever learning how much was in the system beforehand. Assessed with a colored tracer locates leaks but reveals nothing about how much refrigerant is present.
- The HVAC control head is automatically switching modes from panel vents to defrost during heavy acceleration. This is MOST likely caused by:
- A stuck door in the mode housing
- A blown fuse in the panel wiring
- A worn seal in the vent actuator
- A vacuum leak in the supply line
Correct answer: A vacuum leak in the supply line
A vacuum leak in the supply line is the most likely cause: the mode doors are held in position by stored vacuum, manifold vacuum collapses under heavy acceleration, and a leaking supply cannot hold the reserve, so the system falls back to its default defrost setting. A stuck door in the mode housing would lock one setting permanently rather than switch under load. A blown fuse in the panel wiring would disable the controls outright instead of changing modes with throttle position. A worn seal in the vent actuator affects a single outlet, not the whole mode selection.
- When the A/C system is turned on, there is a loud noise from the compressor area, and the belt is observed to be slipping. The MOST likely cause is:
- A seized compressor pulley bearing
- A slipping compressor clutch plate
- A leaking refrigerant service port
- A softened tensioner damper spring
Correct answer: A seized compressor pulley bearing
A seized compressor pulley bearing is the most likely cause, because a bearing that has picked up drags on the pulley and the belt howls and slips as it tries to turn a shaft that no longer spins freely. A slipping compressor clutch plate decouples the load instead of imposing it, so the belt would be relieved rather than stalled. A leaking refrigerant service port lowers the charge, which harms cooling and increases cycling but adds no drag to the belt. A softened tensioner damper spring lets the belt flap and slip whether or not the system has been switched on.
- If the A/C system exhibits poor cooling performance and the sight glass is showing a stream of bubbles at idle, which of the following could be the cause?
- The compressor clutch is faltering
- The refrigerant level is deficient
- The condenser charge is overfilled
- The retained vapor is contaminated
Correct answer: The refrigerant level is deficient
The refrigerant level is deficient is the cause: with too little charge the liquid line never fills completely, so vapor passes the glass as a continuous stream of bubbles and cooling capacity falls away. The compressor clutch is faltering would show as intermittent engagement and cycling rather than a steady bubble stream. The condenser charge is overfilled raises head pressure and normally leaves the glass clear of bubbles. The trapped vapor is contaminated also hurts performance, but air in the system is identified by comparing pressure against temperature, not by bubbles at idle.
- A technician is diagnosing an HVAC issue where the heater does not provide sufficient warmth. After verifying proper coolant level and thermostat operation, the NEXT step should be to:
- Replace the heater core unit
- Flush the cooling loop lines
- Test the heater valve travel
- Check the blend door linkage
Correct answer: Test the heater valve travel
Test the heater valve travel is the next step: with coolant level and thermostat already confirmed, the valve that admits hot coolant to the core is the next thing standing between engine heat and the cabin, and it can be checked without removing anything. Replace the heater core unit commits to a large job before the supply of hot coolant has been proven. Flush the cooling loop lines treats a restricted core that nothing has yet shown to be restricted. Check the blend door linkage belongs after the coolant side is cleared, since a cold core makes any door position irrelevant.
- When a vehicle's interior smells like antifreeze and the windows fog up when the heater is turned on, this is typically indicative of:
- A fouled heater filter
- A topped overflow tank
- A thin coolant mixture
- A ruptured heater core
Correct answer: A ruptured heater core
A ruptured heater core is what this points to: coolant escaping inside the case is blown out of the vents as a warm mist, which both smells of antifreeze and condenses on the glass as a greasy film. A fouled heater filter restricts airflow and may smell stale, but it releases no antifreeze into the cabin. A topped overflow tank pushes coolant out at the cap, under the bonnet rather than inside the vehicle. A thin coolant mixture lowers freeze protection without putting any liquid into the passenger compartment.
- The A/C compressor cycles on and off too frequently, known as short cycling. This condition is MOST often caused by:
- A blocked expansion valve strainer
- A sticking pressure cycling switch
- An overcharged system pushing high
- A refrigerant charge running short
Correct answer: A refrigerant charge running short
A refrigerant charge running short is the usual cause. With too little refrigerant, low-side pressure falls to the cut-out point almost as soon as the compressor engages, so the low-pressure switch drops the clutch, pressure recovers, and the clutch re-engages, giving the rapid on/off pattern. A blocked expansion valve strainer starves the evaporator but produces steady poor cooling and a frosted or iced coil, not rapid clutch cycling. A sticking pressure cycling switch holds the clutch continuously on or continuously off rather than speeding the cycle up. An overcharged system pushing high raises head pressure until the high-pressure cut-out trips, which is a slow, heat-related shutdown.
- A driver complains of rough idle, hesitation under acceleration, and worse fuel economy on a high-mileage vehicle. Which engine component is the MOST likely cause and a normal maintenance item to inspect?
- Worn or fouled ignition spark plugs
- Scored or seized piston skirt walls
- Burnt or pitted exhaust valve seats
- Snapped or worn timing chain guides
Correct answer: Worn or fouled ignition spark plugs
Worn or fouled ignition spark plugs are the likely cause and the routine maintenance item to inspect. As the electrodes erode the gap widens, the spark weakens and the cylinder misfires under load, which is exactly what rough idle, hesitation on acceleration and falling fuel economy on a high mileage engine describe. Scored or seized piston skirt walls give knocking, oil consumption and lost compression, and no service schedule lists them. Burnt or pitted exhaust valve seats leak compression and call for head work rather than a scheduled inspection. Snapped or worn timing chain guides rattle and can let the timing jump, which is a repair job and not a maintenance item.
- A vehicle uses long-life iridium spark plugs. According to typical manufacturer maintenance schedules, about how often should these plugs be replaced?
- Around every 3,000 to 5,000 prescribed miles
- Roughly every 90,000 to 100,000 driven miles
- Nearly every 12,000 to 15,000 motorway miles
- Almost every 24,000 to 30,000 averaged miles
Correct answer: Roughly every 90,000 to 100,000 driven miles
Roughly every 90,000 to 100,000 driven miles is the widely cited replacement interval for long-life iridium plugs, and the technician should still confirm the figure in the manufacturer's maintenance schedule because some makers specify more and some less. Around every 3,000 to 5,000 prescribed miles is an engine oil interval, not a plug interval, and discarding iridium plugs that often throws away a part designed to last far longer. Nearly every 12,000 to 15,000 motorway miles corresponds to filter and rotation service, far short of iridium plug life. Almost every 24,000 to 30,000 averaged miles is the classic copper-plug interval; iridium is used precisely because it outlasts copper by a wide margin.
- A customer asks how often the engine oil should be changed on a late-model vehicle running synthetic oil. What is the BEST answer for a maintenance technician to give?
- Follow the interval the vehicle salesman claims and the oil bottle imprints, roughly 3,000 to 4,000 miles
- Follow the interval the vehicle dipstick shows and the oil darkness implies, roughly 6,000 to 8,000 miles
- Follow the interval the vehicle builder orders and the oil monitor reports, roughly 5,000 to 10,000 miles
- Follow the interval the vehicle driver presumes and the oil ritual dictates, roughly 2,000 to 3,000 miles
Correct answer: Follow the interval the vehicle builder orders and the oil monitor reports, roughly 5,000 to 10,000 miles
Follow the interval the vehicle builder orders and the oil monitor reports, roughly 5,000 to 10,000 miles, is the best advice: the maintenance schedule and the onboard oil life monitor already account for oil type, engine design and how the car is driven, so they are the authoritative source. Follow the interval the vehicle salesman claims and the oil bottle imprints is wrong because a container label and a counter recommendation know nothing about the vehicle or its duty cycle and cannot override the maker's schedule. Follow the interval the vehicle dipstick shows and the oil darkness implies is wrong because oil darkens as it suspends soot and contaminants, which is the oil doing its job rather than a sign of exhaustion. Follow the interval the vehicle driver presumes and the oil ritual dictates is wrong because a habit carried over from conventional oil ignores both the additive life and the time-based limit.
- A technician is checking the engine oil level with a dipstick. Which procedure produces the most accurate reading?
- Read on quick shutdown, catch the draining sump, react fast, then grab and scan the dipstick
- Peer on frigid metal, raise the closed hood, move hurriedly, then tug and trust the dipstick
- Pour on fresh fluid, fill the drained pan, judge afterward, then dip and accept the dipstick
- Park on flat ground, halt the warm motor, wait patiently, then wipe and recheck the dipstick
Correct answer: Park on flat ground, halt the warm motor, wait patiently, then wipe and recheck the dipstick
Park on flat ground, halt the warm motor, wait patiently, then wipe and recheck the dipstick is the accurate procedure: flat ground keeps the pan level, and the short wait lets oil in the heads and galleries drain back so the pan holds its true volume. Read on quick shutdown, catch the draining sump, react fast is wrong because oil is still returning and the reading comes out falsely low. Peer on frigid metal, raise the closed hood, move hurriedly is wrong because it skips the level-surface requirement, and a reading taken wherever the car happened to stop can be off by a lot. Pour on fresh fluid, fill the drained pan, judge afterward is wrong because oil must be measured before any is added, or the engine ends up overfilled.
- A vehicle owner asks what engine oil viscosity, such as the numbers in 5W-30, actually means. Which explanation is correct?
- The W number grades cold-start flow, and the second figure sets thickness once fully heated
- The W number counts crankcase quarts, and the second figure sets refill volume once drained
- The W number marks pigment shading, and the second figure sets additive dosage once blended
- The W number ranks branded quality, and the second figure sets overall scores once compared
Correct answer: The W number grades cold-start flow, and the second figure sets thickness once fully heated
The W number grades cold-start flow, and the second figure sets thickness once fully heated, is the correct reading of a multi-grade rating such as 5W-30: the W stands for winter, a lower first number means the oil still flows at cold start when most wear happens, and the second number describes viscosity at operating temperature. The W number counts crankcase quarts is wrong because capacity is a separate figure printed in the service information and has nothing to do with the grade. The W number marks pigment shading is wrong because neither figure describes color or the additive package. The W number ranks branded quality is wrong because a heavier grade is only better when the manufacturer specifies it; using a thicker oil than specified can slow flow at start-up and starve the engine.
- A customer wants to know how to safely check the engine coolant level. What is the correct maintenance practice?
- Unscrew the radiator at its brassy and heated cap while the engine idles hot
- Inspect the reservoir at its cold and hot marks while the engine stands cool
- Bleed the system at its upper and lower hoses while the engine warms quickly
- Splash the cylinder at its bare and painted metal while the engine glows hot
Correct answer: Inspect the reservoir at its cold and hot marks while the engine stands cool
Inspect the reservoir at its cold and hot marks while the engine stands cool is the correct practice, because the translucent overflow or expansion tank is marked for both conditions, so the level can be judged without ever opening a pressurized circuit. Unscrew the radiator at its brassy and heated cap while the engine idles hot is unsafe, since releasing a hot cap lets superheated coolant flash to steam and spray the technician. Bleed the system at its upper and lower hoses while the engine warms quickly is a repair step performed after a refill, not a way to read the level. Splash the cylinder at its bare and painted metal while the engine glows hot risks thermal shock that can crack a head or block, and it measures nothing.
- A customer wants to know the difference between a serpentine belt and a timing belt. Which statement correctly distinguishes them?
- The serpentine belt hides below shielded housings, while the timing belt meets grit and dirt
- The serpentine belt doubles under supplier labels, while the timing belt shares job and name
- The serpentine belt spins with bolted accessories, while the timing belt links crank and cam
- The serpentine belt meshes with toothed sprockets, while the timing belt rides on plain rims
Correct answer: The serpentine belt spins with bolted accessories, while the timing belt links crank and cam
The serpentine belt spins with bolted accessories, while the timing belt links crank and cam, is the correct distinction: the serpentine belt drives the alternator, power steering pump and air conditioning compressor on the outside of the engine, and the timing belt keeps the crankshaft and camshaft turning in step so valve events match piston position. The serpentine belt hides below shielded housings, while the timing belt meets grit and dirt reverses the arrangement, since the serpentine belt is the exposed one and the timing belt runs behind a cover. The serpentine belt doubles under supplier labels, while the timing belt shares job and name treats one belt as two names when they are two physically different belts doing two different jobs. The serpentine belt meshes with toothed sprockets, while the timing belt rides on plain rims puts the teeth on the wrong belt, since the toothed belt is the one that must hold cam timing.
- A driver asks what the thermostat in their car's cooling system does. Which statement is correct?
- It energizes radiator fans to drive external air rearward
- It contains system pressure to raise boiling point higher
- It registers reservoir levels to warn drivers about leaks
- It meters coolant flow to hold engine running temperature
Correct answer: It meters coolant flow to hold engine running temperature
It meters coolant flow to hold engine running temperature is the thermostat's job: it stays shut while the engine is cold so warm up is quick, then opens to admit flow to the radiator once the calibrated temperature is reached, holding the engine in its efficient band. It energizes radiator fans to drive external air rearward describes the fan relay or control module. It contains system pressure to raise boiling point higher describes the radiator or reservoir cap, whose spring loaded seal lifts the boiling point. It registers reservoir levels to warn drivers about leaks describes a coolant level sensor, a separate device with no control over flow.
- A vehicle runs cooler than normal on the temperature gauge, the heater is slow to warm up, and fuel economy has dropped. A maintenance technician should suspect which condition?
- A thermostat holding open
- A blocked intake strainer
- A rattling camshaft chain
- An overcharged A/C system
Correct answer: A thermostat holding open
A thermostat holding open matches all three complaints. With the valve held open, coolant runs to the radiator continuously, so the engine never reaches its calibrated temperature, the gauge reads low, the heater core never receives hot coolant, and the control module keeps the mixture rich for a cold engine, which costs fuel. A blocked intake strainer cuts airflow and power but does not change coolant temperature. A rattling camshaft chain signals a stretched chain or a failing tensioner and shows as noise and cam timing codes. An overcharged A/C system raises refrigerant pressure and hurts cabin cooling without lowering engine coolant temperature.
- A customer asks what the PCV (positive crankcase ventilation) valve does. Which answer is correct?
- The valve routes heated coolant from the block into the core
- The valve sends escaped vapors from the sump into the intake
- The valve forces metered fuel from the rails into the engine
- The valve admits burnt exhaust from the pipe into the plenum
Correct answer: The valve sends escaped vapors from the sump into the intake
The valve sends escaped vapors from the sump into the intake is what positive crankcase ventilation does. Combustion pressure forces some gas past the rings into the crankcase, and intake vacuum pulls those vapors out through the valve to be burned, which keeps pressure and sludge from building and keeps the vapors out of the atmosphere. The valve routes heated coolant from the block into the core describes a heater control valve. The valve forces metered fuel from the rails into the engine describes injector delivery, which the pump, regulator and control module manage. The valve admits burnt exhaust from the pipe into the plenum describes exhaust gas recirculation, a separate emissions device.
- A vehicle shows reduced power, poor acceleration, lower fuel economy, and sometimes black smoke. Inspection reveals the engine air filter is dark and packed with debris. What is the BEST description of this condition?
- A stuck thermostat cooling combustion, which warrants prompt maintenance
- A cracked diaphragm venting crankcase, which warrants prompt diagnostics
- A choked element strangling induction, which warrants prompt replacement
- A settled dusting darkening filaments, which warrants prompt observation
Correct answer: A choked element strangling induction, which warrants prompt replacement
A choked element strangling induction, which warrants prompt replacement, is the best description. A filter packed with debris cannot pass enough clean air, so the engine runs short of oxygen for the fuel delivered, which gives exactly the reported loss of power, sluggish acceleration, poorer economy and occasional black smoke, and a new element restores the airflow. A stuck thermostat cooling combustion, which warrants prompt maintenance, would show as a low gauge reading and weak cabin heat and cannot be read from a dirty filter. A cracked diaphragm venting crankcase, which warrants prompt diagnostics, belongs to crankcase ventilation faults, which give oil leaks, sludge or a rough idle instead. A settled dusting darkening filaments, which warrants prompt observation, understates an element that is dark and packed solid, well past the point where it still flows.
- A driver of a manual-transmission vehicle reports that engine rpm climbs quickly when accelerating uphill, but the vehicle does not speed up at the same rate. Which condition does this BEST describe?
- A crumbling synchro ring
- A rumbling pilot bearing
- A leaking gearbox casing
- A slipping clutch facing
Correct answer: A slipping clutch facing
A slipping clutch facing is the condition described. When the friction facing can no longer hold against the flywheel, engine speed climbs while road speed lags, and the mismatch is worst under load such as a hill or hard acceleration. A crumbling synchro ring shows up as grinding or baulking during a shift, not as a steady rpm-to-speed mismatch in gear. A rumbling pilot bearing makes noise with the clutch pedal down or during gear changes and does not affect torque transfer. A leaking gearbox casing lowers lubricant level and eventually causes gear noise and wear, but a gearbox low on oil still transmits torque, so it does not produce this rising-rpm complaint.
- During a routine inspection, a technician finds grease slung around the inside of a front wheel well and a small tear in the outer CV boot, but the customer reports no noise yet. What is the BEST description of why the boot must be replaced promptly?
- The boot seals lubricant tightly, so a tear invites abrasive contaminants
- The boot transmits driveline torsion, so a tear invites halfshaft bending
- The boot shields spindle bearings, so a tear invites unlubricated rollers
- The boot regulates differential fluid, so a tear invites housing shortage
Correct answer: The boot seals lubricant tightly, so a tear invites abrasive contaminants
The boot seals lubricant tightly, so a tear invites abrasive contaminants, is why it must be replaced promptly. Grease slings out through even a small split while road grit and water are drawn in, and that mixture laps the balls and races like sandpaper, so the joint is being destroyed well before it starts clicking. The boot transmits driveline torsion is false: the boot is a flexible rubber or thermoplastic cover and carries no torque at all, which is the shaft's job. The boot shields spindle bearings is false because the wheel bearing has its own seals and sits outboard of the joint. The boot regulates differential fluid is false because the joint is packed with grease and is not connected to the axle housing oil.
- A customer asks the difference between an open differential and a limited-slip differential. Which statement BEST explains how a limited-slip unit behaves when one drive wheel is on a slippery surface?
- It bolts axles to the wheel with permanent lockup
- It hands torque to the wheel with dependable grip
- It floods power to the wheel with worthless spins
- It cuts drive to the wheel with vanished adhesion
Correct answer: It hands torque to the wheel with dependable grip
It hands torque to the wheel with dependable grip is what a limited-slip unit does. An open differential follows the path of least resistance, so a tire on ice spins freely and the gripping tire receives almost nothing; the clutches, cones or gears in a limited-slip unit resist that speed difference and keep driving the tire that can still use the torque. It bolts axles to the wheel with permanent lockup describes a fully locked or spool differential, which a limited-slip unit is not, and permanent lockup would fight the car in every corner. It floods power to the wheel with worthless spins describes the open differential behavior the limited-slip design exists to prevent. It cuts drive to the wheel with vanished adhesion is false because no differential disconnects a wheel from its shaft.
- A manual-transmission vehicle is due for a fluid change. Which practice is the MOST correct when performing a manual transmission fluid change?
- Use the fluid stock and dosage that the automatics accept
- Use the fluid leakage and overflow that the plug provides
- Use the fluid grade and quantity that the maker specifies
- Use the fluid seal and lifetime that the designer implies
Correct answer: Use the fluid grade and quantity that the maker specifies
Use the fluid grade and quantity that the maker specifies is the correct practice. Manual gearboxes are built around a named lubricant, which may be a gear oil, an engine oil or a dedicated manual transmission fluid, and both the specification and the fill quantity come from the service information. Use the fluid stock and dosage that the automatics accept is wrong because automatic transmission fluid suits only the gearboxes that call for it, and the wrong friction and viscosity package causes notchy shifting and wear. Use the fluid leakage and overflow that the plug provides is wrong because the fill-plug level is only valid at the stated temperature and vehicle attitude. Use the fluid seal and lifetime that the designer implies is wrong because even a fill-for-life unit still has a checking procedure, and level must be verified rather than assumed.
- A front-wheel-drive car has non-directional, same-size tires. Which rotation pattern is generally recommended for this vehicle?
- Rears progress directly onward, and fronts swivel toward abandoned positions
- Fronts transfer laterally sidewards, and rears duplicate single axle motions
- Fronts retreat rearwards beside lone pathways, and rears advance identically
- Fronts travel straight rearward, and rears cross diagonally opposite corners
Correct answer: Fronts travel straight rearward, and rears cross diagonally opposite corners
Fronts travel straight rearward, and rears cross diagonally opposite corners, is the forward cross pattern recommended for a front-wheel-drive car on non-directional, same-size tires. The drive tires wear fastest, so they are moved straight back, and the lightly worn rears are crossed forward to even the wear out. Rears progress directly onward, and fronts swivel toward abandoned positions is the rearward cross, which belongs to rear-wheel-drive and four-wheel-drive vehicles. Fronts transfer laterally sidewards, and rears duplicate single axle motions keeps each tire on its own axle, so the heavy front wear is never shared with the rear. Fronts retreat rearwards beside lone pathways, and rears advance identically keeps every tire on its own side and skips the crossing that evens out camber-related wear.
- A vehicle is fitted with directional tires marked with a rotation-direction arrow on the sidewall. How should these be rotated?
- Tires swap between front and rear stations along one side
- Tires swap between left and right wheels across one shaft
- Tires swap between near and far ends through one diagonal
- Tires swap between road and spare hubs within one journey
Correct answer: Tires swap between front and rear stations along one side
Tires swap between front and rear stations along one side is how directional tires are rotated. The sidewall arrow fixes the direction each tire must turn, so a tire can only move forward or back on the side it is already fitted to. Tires swap between left and right wheels across one shaft would reverse the rotation direction of both tires on that axle, which spoils wet grip and noise behavior. Tires swap between near and far ends through one diagonal also moves tires to the opposite side and reverses them. Tires swap between road and spare hubs within one journey is wrong because a full-size spare can only join the pattern if it matches and if the direction is preserved, and it does nothing to answer how directional tires move.
- A technician is asked to set the tires to the correct inflation. Where is the recommended (placard) cold tire pressure for the vehicle found?
- On the vehicle laden mass at the public weighbridge
- On the vehicle information sticker at the door jamb
- On the vehicle tire sidewall at the maximum marking
- On the vehicle wheel casting at the stamped borders
Correct answer: On the vehicle information sticker at the door jamb
On the vehicle information sticker at the door jamb is where the recommended cold inflation pressure is published, and the same figures are repeated in the owner's manual; on some cars the label sits in the glovebox or on the fuel filler flap instead. On the vehicle laden mass at the public weighbridge is wrong because technicians do not calculate pressure from a weight reading, the manufacturer has already done that work. On the vehicle tire sidewall at the maximum marking is wrong because the moulded number is the maximum the casing may hold, not the pressure this vehicle wants. On the vehicle wheel casting at the stamped borders is wrong because the numbers stamped there give rim size and offset.
- A driver asks what TPMS does. Which statement best describes a tire pressure monitoring system?
- It measures 4 channels and gauges the tread past 3 millimeters
- It disregards 4 tires and monitors the spare beyond 1 mounting
- It samples 4 corners and alerts the motorist around 25 percent
- It pressurizes 4 hoses and reinflates the casings amid 2 stops
Correct answer: It samples 4 corners and alerts the motorist around 25 percent
It samples 4 corners and alerts the motorist around 25 percent describes a tire pressure monitoring system: United States rules require the lamp to come on when a tire falls roughly 25 percent below the placard cold pressure, whether the system reads pressure directly from in-wheel senders or infers it from wheel speed. It measures 4 channels and gauges the tread past 3 millimeters is wrong because no production monitor reads tread depth. It disregards 4 tires and monitors the spare beyond 1 mounting is wrong because the road wheels are exactly what the system watches, and only a few vehicles monitor the spare at all. It pressurizes 4 hoses and reinflates the casings amid 2 stops is wrong because monitoring is all the system does; it has no compressor and cannot add air.
- A car uses an indirect TPMS. After the customer adds air and rotates the tires, the TPMS light comes on. What is the correct next step?
- Exchange the TPMS senders so fresh battery packs respond
- Replace the TPMS module so fresh network wiring connects
- Recharge the TPMS circuit so fresh gas pressure rebuilds
- Relearn the TPMS baseline so fresh rolling speeds settle
Correct answer: Relearn the TPMS baseline so fresh rolling speeds settle
Relearn the TPMS baseline so fresh rolling speeds settle is the correct next step. An indirect system infers a low tire from how fast each wheel turns, so the moment pressures change or tires swap corners, the stored reference no longer matches and the lamp stays on until the reset procedure captures a new baseline. Exchange the TPMS senders so fresh battery packs respond is impossible on this car, because an indirect system has no in-wheel senders. Replace the TPMS module so fresh network wiring connects treats a routine calibration as a hardware failure and would leave the same stale reference. Recharge the TPMS circuit so fresh gas pressure rebuilds confuses tire monitoring with air conditioning service, which has no bearing on the warning lamp.
- A customer reports clunking over bumps, looseness in the front end, and uneven inside-edge tire wear. Which worn component is the MOST likely cause?
- A slack ball joint socket
- A broken sway bar bushing
- A crushed strut top mount
- A pitted rear hub bearing
Correct answer: A slack ball joint socket
A slack ball joint socket is the most likely cause. Once the stud has room to move in its socket the wheel can knock over bumps, the front end feels loose, and the camber and toe wander enough to scrub the inner edge of the tread. A broken sway bar bushing rattles over bumps too, but it carries no alignment load, so it cannot produce the inside-edge wear. A crushed strut top mount usually announces itself as a bind or a groan while the steering is turned rather than a bump clunk plus edge wear. A pitted rear hub bearing gives a speed-related growl at the back of the car and has no effect on front-end geometry.
- To check a loaded ball joint for vertical (axial) play, how should the suspension be supported before measuring?
- Pull the road wheels, benching the joint, then gauge play
- Prop the control arms, loading the joint, then gauge play
- Press the brake pedal, rocking the joint, then gauge play
- Drop the hubs loosely, hanging the joint, then gauge play
Correct answer: Prop the control arms, loading the joint, then gauge play
Prop the control arms, loading the joint, then gauge play is the right set-up for a loaded joint. The arm must be supported so the joint still carries the weight of the vehicle, and a dial indicator or careful prying then shows axial and radial movement that can be compared with the specification. Pull the road wheels, benching the joint, then gauge play removes the joint from the loading that the test depends on. Press the brake pedal, rocking the joint, then gauge play is a steering-linkage dry-park check and tells nothing about vertical play in a load-carrying joint. Drop the hubs loosely, hanging the joint, then gauge play unloads a loaded design completely, and an unloaded joint can measure tight while it is badly worn.
- A wear-indicator (greaseable) ball joint will not accept grease from a grease gun because the fitting will no longer couple. What does this indicate on this style of joint?
- The joint has drifted off and needs aligning
- The joint has split open and needs resealing
- The joint has worn loose and needs replacing
- The joint has settled down and needs nothing
Correct answer: The joint has worn loose and needs replacing
The joint has worn loose and needs replacing is what the fitting is telling the technician. On this wear-indicator design the grease fitting itself is the gauge: it stands proud while the joint is serviceable and recedes into the housing as the stud wears, so once a grease gun can no longer couple to it the joint has passed its limit. The joint has drifted off and needs aligning is wrong because alignment is measured on a rack and has nothing to do with whether a fitting couples. The joint has split open and needs resealing is wrong because a torn boot is a separate finding and would not pull the fitting down into the housing. The joint has settled down and needs nothing is wrong because a healthy joint of this type takes grease normally.
- A driver complains of a clunk or knock when steering and a loud popping during sharp turns, plus wandering steering. Inspection should focus on which component?
- The upper idler arm bush
- The rack clamp seat pads
- The strut top mount ring
- The outer tie rod joints
Correct answer: The outer tie rod joints
The outer tie rod joints deserve the closest inspection. They are the last link between the steering rack and the knuckle, so once the ball and socket inside them develops clearance the wheel can move independently of the steering wheel, which shows up as knocking while turning, wandering on the straight and feathered tread wear. The upper idler arm bush belongs to a parallelogram linkage, which a rack-and-pinion car does not have, and it would not be the first place to look. The rack clamp seat pads let the whole rack shift under load and give a rattle rather than the described sequence. The strut top mount ring binds or groans when the steering is turned but has no effect on toe or on steering slack.
- Both a worn ball joint and a worn tie rod end can feel loose in the front end. Which symptom most specifically points to a tie rod end rather than a ball joint?
- Free play noted at the steering wheel edge
- Sharp knocks heard at the bumpy road crest
- Low ride height seen at the sagging corner
- Dry squeaks noticed at the strut top mount
Correct answer: Free play noted at the steering wheel edge
Free play noted at the steering wheel edge points specifically at a tie rod end. A tie rod sits inside the steering linkage, so slack in it shows up directly as movement of the rim that never reaches the road wheels. Sharp knocks heard at the bumpy road crest describe a suspension pivot loading and unloading, which is the ball joint pattern rather than the tie rod pattern. Low ride height seen at the sagging corner is a spring fault and tells nothing about either joint. Dry squeaks noticed at the strut top mount come from the upper bearing or its isolator and are not a measure of linkage slack.
- A customer asks what a wheel alignment actually adjusts. Which answer is correct?
- The rotating assembly covering weights, rims and clamps
- The suspension geometry covering camber, caster and toe
- The braking flatness covering rotors, pads and spindles
- The inflation level covering placards, dials and valves
Correct answer: The suspension geometry covering camber, caster and toe
The suspension geometry covering camber, caster and toe is what an alignment sets. The technician adjusts how each wheel stands relative to the body and the road so the tires wear evenly, the car tracks straight and the steering returns to center. The rotating assembly covering weights, rims and clamps is wheel balancing, a separate machine and a separate service that corrects mass distribution rather than angle. The braking flatness covering rotors, pads and spindles is measured with a dial indicator during a brake service and is not touched on an alignment rack. The inflation level covering placards, dials and valves is set before alignment because pressure affects the readings, but it is not what the alignment itself adjusts.
- On an alignment readout, which set of definitions is correct for camber, caster, and toe?
- Camber gauges pivot raking ahead, caster gauges wheel tilt aside, and toe gauges track lines above
- Camber gauges speed drifting ahead, caster gauges timing lag aside, and toe gauges load sway above
- Camber gauges wheel leaning ahead, caster gauges pivot rake aside, and toe gauges tread aims above
- Camber gauges frame sagging ahead, caster gauges hub spacing aside, and toe gauges rim droop above
Correct answer: Camber gauges wheel leaning ahead, caster gauges pivot rake aside, and toe gauges tread aims above
Camber gauges wheel leaning ahead, caster gauges pivot rake aside, and toe gauges tread aims above is the correct set: camber is the inward or outward tilt of the wheel seen from the front, caster is the forward or rearward tilt of the steering axis seen from the side, and toe is whether the wheels point in or out seen from above. Camber gauges pivot raking ahead, caster gauges wheel tilt aside swaps the first two definitions, since the steering axis tilt is caster. Camber gauges speed drifting ahead, caster gauges timing lag aside attaches these names to quantities no alignment rack measures. Camber gauges frame sagging ahead, caster gauges hub spacing aside confuses the three angles with ride height, track width and wheel offset.
- A technician needs to explain the difference between camber and toe to a customer. Which statement is accurate?
- Camber tips pivot shafts rearwardly, while toe swings wheel castings outwardly
- Camber tips body clearance upwardly, while toe swings steering wheels homeward
- Camber tips wheel spacings inwardly, while toe swings steering spokes sideways
- Camber tips wheel crowns vertically, while toe swings tread noses horizontally
Correct answer: Camber tips wheel crowns vertically, while toe swings tread noses horizontally
Camber tips wheel crowns vertically, while toe swings tread noses horizontally is the accurate contrast to give a customer: camber is the vertical lean of the wheel seen from the front of the car, and toe is the horizontal direction the wheels point seen from above. Camber tips pivot shafts rearwardly, while toe swings wheel castings outwardly hands camber the steering pivot rake that belongs to caster and gives the wheel lean to toe. Camber tips body clearance upwardly, while toe swings steering wheels homeward attaches ride height to camber, which the springs set, and self centring to toe, which caster provides. Camber tips wheel spacings inwardly, while toe swings steering spokes sideways confuses camber with wheel offset and toe with a crooked steering wheel, which is only a symptom of a toe setting.
- Center-tread wear with good shoulders most often indicates which condition?
- Constant overinflation, arching the tread crowns outwardly
- Habitual underinflation, flattening the outer shoulder rib
- Excessive camber, scrubbing the innermost sidewall banding
- Slackened steering linkages, feathering the rubbery edging
Correct answer: Constant overinflation, arching the tread crowns outwardly
Constant overinflation, arching the tread crowns outwardly, is what center wear with healthy shoulders indicates. Too much pressure bows the crown of the tread out so the middle of the contact patch carries the load while the shoulders barely touch. Habitual underinflation, flattening the outer shoulder rib produces the opposite picture, with both shoulders worn and the center still good. Excessive camber, scrubbing the innermost sidewall banding wears one edge only, so it cannot leave both shoulders healthy. Slackened steering linkages, feathering the rubbery edging leave a saw-toothed pattern across the blocks rather than a smooth band of center wear.
- A customer asks what the sway bar (stabilizer bar) does. Which description is correct?
- It squeezes the inner and outer races to retain hub bearings
- It connects the left and right corners to restrain body roll
- It aims the back and rear knuckles to steer following wheels
- It absorbs the road and bump impacts to replace coil springs
Correct answer: It connects the left and right corners to restrain body roll
It connects the left and right corners to restrain body roll is what a sway bar, also called a stabilizer or anti-roll bar, does. It is a torsion spring tying the two sides together, so when the body leans in a corner and one side compresses more than the other the bar twists and resists that difference. It squeezes the inner and outer races to retain hub bearings describes the hub, spindle nut and bearing retainer instead. It aims the back and rear knuckles to steer following wheels describes a rear-steer system, which a stabilizer bar has nothing to do with. It absorbs the road and bump impacts to replace coil springs is wrong because the bar does nothing on a bump that lifts both wheels equally, and the springs still carry the vehicle.
- A customer asks the difference between a shock absorber and a strut. Which statement is correct?
- A strut rests rearward and inboard, while a shock stays forward
- A strut wanders loosely and drifts, while a shock bears burdens
- A strut supports springs and loads, while a shock damps motions
- A strut mirrors branding and labels, while a shock repeats them
Correct answer: A strut supports springs and loads, while a shock damps motions
A strut supports springs and loads, while a shock damps motions, is the correct distinction. A strut is a structural member of the suspension: it usually carries the coil spring, often provides the upper steering pivot, and it damps as well, so removing one takes the corner apart. A shock absorber only controls spring oscillation and carries no vehicle weight. A strut rests rearward and inboard, while a shock stays forward is false because either can appear at either end depending on the design. A strut wanders loosely and drifts, while a shock bears burdens reverses the two roles. A strut mirrors branding and labels, while a shock repeats them is false because they are different parts, not two trade names for one part.
- A car bounces several times after going over a bump, dives heavily under braking, and shows cupped tire wear. Which conclusion is best supported?
- The casings have hardened and should be deflated
- The angles have widened and should be readjusted
- The impellers have worn and should be overhauled
- The struts have weakened and should be exchanged
Correct answer: The struts have weakened and should be exchanged
The struts have weakened and should be exchanged is the conclusion this evidence supports. Continued bouncing after a bump, heavy nose dive under braking and cupped tread all say the damper can no longer control the spring, and a wheel that skips as it oscillates scallops the tread. The casings have hardened and should be deflated is wrong because over-pressure wears the center of the tread evenly and does not add bounce or dive. The angles have widened and should be readjusted is wrong because a toe error feathers the tread without affecting body control. The impellers have worn and should be overhauled points at the power steering pump, which would whine and stiffen the steering rather than upset the ride.
- A technician must decide whether shock absorbers should be replaced. Which finding most justifies replacement?
- Oily streaks weeping around the shock cylinder, plus feeble bouncing control
- Roadway powder clinging beside the shock housing, plus adequate ride comfort
- Motorway miles building behind the shock piston, plus routine highway travel
- Calendar years passing beneath the shock fitting, plus firm damping response
Correct answer: Oily streaks weeping around the shock cylinder, plus feeble bouncing control
Oily streaks weeping around the shock cylinder, plus feeble bouncing control, is the finding that justifies replacement. A shock works by forcing hydraulic fluid through valving, so a wet body means the seal has gone and the fluid it needs has escaped, and the poor bounce test confirms the loss has reached the point of affecting the ride. Roadway powder clinging beside the shock housing, plus adequate ride comfort is just dirt on a working unit. Motorway miles building behind the shock piston, plus routine highway travel is ordinary service and no evidence of failure. Calendar years passing beneath the shock fitting, plus firm damping response argues against replacement, because age alone condemns nothing when the damper still controls the spring.
- A vehicle has a steady humming/growling that rises and falls with road speed and changes pitch when the car is steered side to side during a road test. Which component is MOST likely worn?
- A perished outboard axle boot
- A roughened front hub bearing
- A howling rearward drive gear
- A dragging rearmost brake pad
Correct answer: A roughened front hub bearing
A roughened front hub bearing is the most likely worn part. Damaged races and rollers produce a hum or growl that tracks road speed, and steering left and right shifts vehicle weight onto and off that bearing, so the noise gets louder or quieter with the direction of the turn. A perished outboard axle boot leads to a clicking joint on tight turns, not a steady speed-related growl. A howling rearward drive gear rises with speed too, but it responds to throttle load rather than to cornering, and it comes from the differential rather than a wheel. A dragging rearmost brake pad gives a scrape or squeal that changes when the brake is applied, and it does not follow steering input.
- Technician A says a worn wheel bearing usually makes a steady speed-related hum that changes with cornering load. Technician B says a worn ball joint usually makes a clunk over bumps rather than a steady hum. Who is correct?
- Technician A only
- Technician B only
- Both Technician A and Technician B
- Neither technician
Correct answer: Both Technician A and Technician B
Both Technician A and Technician B is the answer, because each statement holds up on its own. Technician A is correct: a worn wheel bearing produces a continuous hum or growl that rises and falls with road speed, and because cornering transfers weight onto or off the bearing, the noise grows louder or quieter as the car is steered left and right. Technician B is also correct: a worn ball joint is a pivot with clearance in it, so it knocks as the suspension loads and unloads over a bump and gives an intermittent clunk rather than a steady hum. Technician A only leaves Technician B's accurate description unaccounted for, Technician B only does the same to Technician A, and Neither technician denies two descriptions that are the standard way to separate a bearing complaint from a joint complaint.
- A customer reports hard steering, a whining power steering pump, and fluid pooling under the front of the car. Which is the MOST likely cause?
- A collapsed bushing that has restricted the movement
- A slackened tensioner that has burnished the pulleys
- A fragmented bearing that has roughened the raceways
- A hydraulic leakage that has exhausted the reservoir
Correct answer: A hydraulic leakage that has exhausted the reservoir
A hydraulic leakage that has exhausted the reservoir ties all three complaints together, since a pump that has lost fluid draws air instead and whines, a low reservoir cannot supply the flow that makes assist, and the puddle at the front is the leak itself. A collapsed bushing that has restricted the movement stiffens the wheel but leaves no puddle and makes no whine. A slackened tensioner that has burnished the pulleys produces belt noise without emptying anything onto the ground. A fragmented bearing that has roughened the raceways howls at road speed and has no bearing on assist or on fluid loss.
- During a suspension inspection a technician finds a cracked, mushy rubber control arm bushing. What is the primary purpose of a control arm bushing?
- To cushion and locate the pivots while damping tremors
- To carry and direct the fluids while feeding cylinders
- To create and boost the assistance while driving pumps
- To watch and signal the pressure while warning drivers
Correct answer: To cushion and locate the pivots while damping tremors
To cushion and locate the pivots while damping tremors is the bushing's primary purpose. It holds the arm in its correct position at the frame pivot, allows the controlled arc the suspension needs, and isolates road noise and vibration from the body; once the rubber cracks and goes mushy the arm can shift, alignment drifts and clunks appear. To carry and direct the fluids while feeding cylinders describes brake hoses and lines. To create and boost the assistance while driving pumps describes the power steering pump and its drive. To watch and signal the pressure while warning drivers describes tire pressure monitoring, which has no connection to a suspension bushing.
- A technician is bleeding the hydraulic brakes using the two-person manual method. In what order should the wheels generally be bled on a typical diagonal-split system, and what is the basic procedure at each wheel?
- Bleed the wheel farthest from the master cylinder, closing the bleeder screw with the pedal held down
- Open the four wheel bleeders together, letting gravity pull air from the lines with the pedal resting
- Pump the pedal harder, drawing spent fluid from the wheel cylinders with the filler cap torqued tight
- Vent the wheel nearest the pedal, purging air backward from the calipers with the outlet valve closed
Correct answer: Bleed the wheel farthest from the master cylinder, closing the bleeder screw with the pedal held down
The correct procedure is to bleed the wheel farthest from the master cylinder, closing the bleeder screw with the pedal held down, so that air is never drawn back past the threads when the helper lifts a foot; the reservoir is topped up between wheels. Opening the four wheel bleeders together lets gravity pull air inward instead of expelling it. Pumping the pedal harder with the filler cap torqued tight starves the master cylinder and churns the fluid. Working the wheel nearest the pedal with the outlet valve closed moves no fluid whatsoever.
- A customer asks the difference between the disc brakes on the front of their car and the drum brakes on the rear. Which statement best describes a key advantage of disc brakes over drum brakes?
- Disc brakes house the shoes and wheel cylinders, giving firmer grip and cooler running than drums
- Disc brakes leave the rotor surfaces open and shed heat rapidly, resisting fade longer than drums
- Disc brakes enclose the pads inside the sealed housing and trap warmth, fading quicker than drums
- Disc brakes occupy the rear axle and drums the front hubs, clamping noticeably harder than rotors
Correct answer: Disc brakes leave the rotor surfaces open and shed heat rapidly, resisting fade longer than drums
The accurate statement is that disc brakes leave the rotor surfaces open and shed heat rapidly, resisting fade longer than drums, because the exposed rotor sits in moving air while a drum encloses its friction surfaces. Shoes and wheel cylinders belong to the drum assembly rather than the disc assembly, so that description reverses the hardware and the grip claim with it. Disc pads are not enclosed inside a sealed housing; that is precisely the drum arrangement which traps warmth. Discs are normally fitted at the front, where load transfer is greatest, so they are not confined to the rear axle.
- A vehicle's owner's manual specifies DOT 3 brake fluid, but the technician only has DOT 4 on hand. Which statement about DOT 3 versus DOT 4 fluid is correct?
- DOT 4 absorbs sooner when cold than DOT 3, risking line corrosion, and both fluids are silicone based
- DOT 4 thins quicker when heated than DOT 3, swelling brake seals, and both fluids are petroleum based
- DOT 4 boils hotter when dry than DOT 3, containing borate additives, and both fluids are glycol based
- DOT 4 discolors slower when aged than DOT 3, masking trapped water, and both fluids are mineral based
Correct answer: DOT 4 boils hotter when dry than DOT 3, containing borate additives, and both fluids are glycol based
The correct statement is that DOT 4 boils hotter when dry than DOT 3, containing borate additives, and both fluids are glycol based, so DOT 4 may generally be used where DOT 3 is specified once the service information is checked. Silicone chemistry belongs to DOT 5, which is kept out of glycol systems entirely, so that pairing is wrong. Petroleum stock is never used for brake fluid because it swells the rubber seals it contacts. Mineral oil likewise belongs to a different class of system, and neither grade is formulated from it.
- A vehicle pulls hard to one side under braking, the affected wheel runs noticeably hotter, and there is uneven pad wear on that corner. Which symptom set most strongly points to a sticking or seized brake caliper?
- One wheel that scratches, chatters, and wears the drum squarely, with a weaker pull
- One wheel that pulses, shimmies, and scores the rotor lightly, with a rhythmic pull
- One wheel that squeals, drips, and soaks the brake hardware, with a noticeable pull
- One wheel that drags, overheats, and wears the pads unevenly, with a continual pull
Correct answer: One wheel that drags, overheats, and wears the pads unevenly, with a continual pull
The symptom set that fits a sticking caliper is one wheel that drags, overheats, and wears the pads unevenly, with a continual pull, because a piston or slide that will not release keeps the friction material loaded at that corner alone. A wheel that scratches and chatters while wearing the drum squarely describes ordinary drum and lining wear, which does not overheat that corner. A wheel that pulses and shimmies while lightly scoring the rotor indicates thickness variation, felt only while the pedal is applied. A wheel that squeals and drips while soaking the brake hardware indicates a leaking wheel cylinder, which loses pressure instead of holding it.
- During routine maintenance, what is the most accurate general guidance for how often brake fluid should be changed, and why?
- Replace the fluid at the manual interval, near the third year, since glycol chemistry slowly draws moisture
- Exchange the fluid at the oil change, near the wheel rotation, since underhood heat discolors the reservoir
- Replenish the fluid at the pedal collapse, near the floor carpet, since shorter travel signals soaked lines
- Retain the fluid at the sealed circuit, near the vehicle life, since closed systems block external dampness
Correct answer: Replace the fluid at the manual interval, near the third year, since glycol chemistry slowly draws moisture
The best guidance is to replace the fluid at the manual interval, near the third year, since glycol chemistry slowly draws moisture out of the air, and wet fluid boils at a lower temperature and corrodes the bores. Tying the change to an oil change or a wheel rotation ignores the published interval and has nothing to do with how the fluid ages. Waiting for the pedal to collapse toward the floor means the damage has already happened. A brake system breathes through the reservoir cap, so it is not closed against external dampness.
- A driver asks how the anti-lock braking system (ABS) keeps the wheels from locking during a hard stop. Which description is correct?
- ABS seizes the wheel parking cables and squeezes the drums, adding pressure near violent braking
- ABS watches the wheel speed sensors and cycles the modulator, easing pressure near sudden lockup
- ABS detects the wheel rain switch and disables the circuit, cutting pressure near moist pavement
- ABS lifts the wheel line force and locks the calipers, holding pressure near complete standstill
Correct answer: ABS watches the wheel speed sensors and cycles the modulator, easing pressure near sudden lockup
The correct description is that ABS watches the wheel speed sensors and cycles the modulator, easing pressure near sudden lockup and then restoring it many times a second so the tire keeps rolling and the driver keeps steering. ABS has no connection to the parking brake cables and never squeezes the drums during a stop. There is no rain switch input; the system works on wet and dry surfaces alike. Lifting line force until the calipers lock is the opposite of what the modulator does.
- After descending a long mountain grade while riding the brakes, a driver reports the pedal feels normal but the vehicle takes much longer to stop. The brake friction surfaces are extremely hot. What is this condition called?
- Brake boil
- Brake bind
- Brake fade
- Brake grab
Correct answer: Brake fade
The condition described is brake fade: prolonged dragging on a long descent drives the friction surfaces so hot that the pad or lining material outgasses and loses its coefficient of friction, so stopping distance grows while the pedal still feels firm and high. Brake boil describes fluid vaporizing in the lines, which gives a soft or sinking pedal rather than a normal one. Brake bind describes a caliper or cable that will not release, which drags one corner and pulls the vehicle. Brake grab describes a sudden bite from contaminated or scored friction material, the opposite of reduced stopping power.
- While inspecting disc brakes during a maintenance service, the technician measures the friction material remaining on the pads. What is the generally accepted guideline for minimum brake pad thickness before replacement?
- Replace the pads once the friction material passes thirteen millimeters, or once the caliper piston stalls
- Replace the pads once the friction material approaches zero millimeters, or once the rotor minimum applies
- Replace the pads once the friction material registers seven millimeters, or once the pedal effort lightens
- Replace the pads once the friction material reaches three millimeters, or once the factory minimum arrives
Correct answer: Replace the pads once the friction material reaches three millimeters, or once the factory minimum arrives
The accepted guideline is to replace the pads once the friction material reaches three millimeters, or once the factory minimum arrives, whichever applies; that is roughly an eighth of an inch of usable material left. Thirteen millimeters is thicker than most new pads, so scrapping there throws away friction material that has barely been used. Letting the material approach zero means the steel plate reaches the rotor, which ruins the rotor and cuts braking badly. Seven millimeters is only about half worn, so replacing there is premature and wastes serviceable lining.
- A customer says the parking brake is not holding the vehicle on an incline, but the foot brake works fine. After confirming the cables and shoes are serviceable, what maintenance step most directly addresses a parking brake that engages too far before holding?
- Adjust the parking brake cables or the rear shoe adjusters, removing the excessive slack
- Bleed the parking brake cables or the front caliper connections, purging the trapped air
- Flush the parking brake fluid or the entire hydraulic circuit, replacing the dark liquid
- Renew the parking brake booster or the master cylinder body, restoring the lost pressure
Correct answer: Adjust the parking brake cables or the rear shoe adjusters, removing the excessive slack
The step that fixes excessive travel before the brake holds is to adjust the parking brake cables or the rear shoe adjusters, removing the excessive slack, because the parking brake is a mechanical linkage that stretches and wears independently of the hydraulic circuit. The parking brake has no hydraulic caliper connections of its own, so bleeding cannot restore its hold. Flushing hydraulic fluid renews the service brake only and does nothing to cable tension. A booster or master cylinder serves foot braking, and the foot brake already works correctly here.
- A technician needs to determine whether a brake rotor can be reused. Where is the minimum (discard) thickness specification for a rotor typically found?
- It is imprinted onto the rotor pad surfaces or boxes, and copied inside the parts catalog
- It is stamped onto the rotor hat or outer edge, and listed inside the service information
- It is halved onto the factory rotor depth or breadth, and rounded inside the shop manuals
- It is engraved onto the rotor wheel studs or bolts, and repeated inside the tire placards
Correct answer: It is stamped onto the rotor hat or outer edge, and listed inside the service information
The discard specification is stamped onto the rotor hat or outer edge, and listed inside the service information, so a technician can read it on the part in hand and confirm it against published data. Nothing about rotor thickness is marked on the pad surface or its carton, which carry friction compound and part numbers instead. The discard figure is a measured engineering limit, never a simple half of the factory rotor depth. Wheel studs and bolts carry no such marking, and the tire placards list pressures and sizes only.
- What is the correct way to measure a brake rotor's thickness to compare it against the discard specification?
- Use the tape measure at several points around the rotor rim, comparing the broadest diameter
- Use the feeler gauge at several points around the rotor surface, measuring the pad clearance
- Use the outside micrometer at several points around the rotor face, noting the thinnest spot
- Use the naked eyeball at several points around the rotor grooves, estimating the wear depths
Correct answer: Use the outside micrometer at several points around the rotor face, noting the thinnest spot
The correct method is to use the outside micrometer at several points around the rotor face, noting the thinnest spot, since only a micrometer resolves the hundredths a discard limit is written to, and repeated readings also expose thickness variation. A tape measure reports outside diameter, which is not the dimension being judged. A feeler gauge measures a gap between two parts, so it cannot report how thick the casting still is. The naked eye cannot resolve tenths of a millimeter, so a visual call on the wear groove is guesswork.
- A customer wants to know what the master cylinder does in their brake system. Which statement best describes its purpose?
- It splits the braking pressure into balanced portions, matching the front and rear demands
- It squeezes the intake air into onboard cylinders, amplifying the brake and clutch efforts
- It converts the axle rotation into electric pulses, guiding the module and solenoid timing
- It turns the pedal force into hydraulic pressure, feeding the calipers and wheel cylinders
Correct answer: It turns the pedal force into hydraulic pressure, feeding the calipers and wheel cylinders
It turns the pedal force into hydraulic pressure, feeding the calipers and wheel cylinders through the brake lines, and most use a tandem bore so a leak in one circuit still leaves partial braking. It splits the braking pressure into balanced portions describes a proportioning or combination valve mounted downstream of it. It squeezes the intake air into onboard cylinders belongs to an air brake system, which a liquid filled light vehicle circuit does not have. It converts the axle rotation into electric pulses describes the speed sensors that report to the antilock module.
- During a drum brake inspection, the technician measures the bonded brake lining (shoe friction material). What general guideline indicates the linings should be replaced?
- The bonded material stands one sixteenth inch above the drum shoe, reaching the factory limit
- The bonded material settles one eighth inch below the rivet heads, approaching the shoe table
- The bonded material clears one quarter inch inside the drum bore, passing the oversize figure
- The bonded material touches one third inch across the drum shell, showing the contact pattern
Correct answer: The bonded material stands one sixteenth inch above the drum shoe, reaching the factory limit
Bonded linings are due for renewal when the bonded material stands one sixteenth inch above the drum shoe, reaching the factory limit, which is roughly 1.6 mm of usable friction material left. The bonded material settles one eighth inch below the rivet heads, approaching the shoe table borrows the riveted lining rule, and a bonded lining carries no rivets to wear down to. The bonded material clears one quarter inch inside the drum bore, passing the oversize figure measures drum wear, which is a separate discard specification for the drum itself. The bonded material touches one third inch across the drum shell, showing the contact pattern reports arc fit rather than how much friction material remains.
- A driver feels a steady pulsation or vibration in the brake pedal and steering wheel only when braking, especially from higher speeds. Which condition most likely explains these symptoms?
- A trapped air pocket or softened fluid column giving sluggish responses
- A distorted rotor or varying disc thickness giving unequal pad contacts
- A shrunken reservoir level or weeping wheel cylinder giving slow return
- A stretched parking cable or frayed handbrake wire giving weakened grip
Correct answer: A distorted rotor or varying disc thickness giving unequal pad contacts
The condition behind a rhythmic beat felt only while braking is a distorted rotor or varying disc thickness giving unequal pad contacts, because high and low spots on the friction surface load and unload the pads once per revolution, so the vibration grows with speed and braking force. A trapped air pocket or softened fluid column gives a soft, sinking pedal instead of a repeating beat. A shrunken reservoir level or weeping wheel cylinder signals a hydraulic leak, which shows up as fluid loss and weak braking. A stretched parking cable or frayed handbrake wire affects holding on a grade, never pedal feel at speed.
- A technician is replacing the disc brake pads on a vehicle that has a single-piston floating caliper. Before installing the new, thicker pads, what step is required to make room for them?
- Loosen the caliper bleeder screw into the tray, draining the master cylinder reservoir for cleaning
- Bleed the caliper piston circuit into the hoses, filling the master cylinder reservoir for pressure
- Compress the caliper piston back into the bore, watching the master cylinder reservoir for overflow
- Pour the fresh brake fluid into the caliper, flooding the master cylinder reservoir for lubrication
Correct answer: Compress the caliper piston back into the bore, watching the master cylinder reservoir for overflow
The step that makes room for the thicker pads is to compress the caliper piston back into the bore, watching the master cylinder reservoir for overflow, since retracting the piston pushes the displaced fluid back up the line and can lift the level past the brim. Loosening the bleeder screw and draining the reservoir admits air and empties the circuit rather than creating clearance. Bleeding a piston circuit is a separate service that never retracts the piston. Adding fresh fluid at the caliper puts more volume into a system that already lacks room.
- During a brake service, the technician notices the brake fluid in the reservoir is dark and the level has dropped slightly since the pads are worn. Why does the fluid level normally fall as disc brake pads wear?
- The master cylinder seals consume fluid, so the barrel absorbs stored volume
- The reservoir cover vents warm vapor, so the level drops through evaporation
- The thinning pads cause suction inside, so the tubing siphons fluid backward
- The caliper pistons extend further outward, so the circuit holds extra fluid
Correct answer: The caliper pistons extend further outward, so the circuit holds extra fluid
The level falls because the caliper pistons extend further outward, so the circuit holds extra fluid out at the wheels as the friction material thins; topping the reservoir without inspecting the pads therefore hides that wear. The master cylinder seals consume fluid is wrong, as the bore and its seals absorb none of the volume they pass. The reservoir cover vents warm vapor to atmosphere, but brake fluid does not evaporate away in any measurable quantity. The thinning pads cause suction inside is wrong, since a sealed hydraulic circuit cannot draw fluid backward out of the reservoir.
- A vehicle equipped with ABS will momentarily pulse the brake pedal and may make a buzzing or grinding noise during a hard stop on a slippery surface. How should a technician respond if a customer reports this?
- Reassure the waiting driver, since the pedal pulse and motor growl mark expected ABS cycling
- Bleed the entire circuit, since the pedal pulse and motor growl reveal lingering ABS bubbles
- Replace the hydraulic pump, since the pedal pulse and motor growl confirm failing ABS valves
- Disable the ABS module, since the pedal pulse and motor growl unsettle the driving customers
Correct answer: Reassure the waiting driver, since the pedal pulse and motor growl mark expected ABS cycling
The right response is to reassure the waiting driver, since the pedal pulse and motor growl mark expected ABS cycling, with the modulator releasing and reapplying pressure many times a second to keep the wheels rolling and steerable. Bleeding treats trapped air, which gives a soft pedal rather than a rapid pulse under a hard stop. Replacing the hydraulic pump chases a failure that has not happened and would not change the cycling anyway. Disabling the module shuts off a safety system merely to silence the sound of that system working.
- A customer reports a battery warning light that glows during driving, dimming headlights at night, and a recently dead battery. Which component is the MOST likely cause of all three symptoms together?
- A grinding starter, the geared cranking motor
- A failing alternator, the belt driven charger
- A corroding relay, the plastic switching unit
- A sticking thermostat, the coolant flow valve
Correct answer: A failing alternator, the belt driven charger
The one part that explains all three complaints together is a failing alternator, the belt driven charger, because it both carries the running electrical load and recharges the battery, so a weak one lights the charging lamp, lets the headlights dim, and leaves the battery to run flat. A grinding starter, the geared cranking motor, works only while cranking and cannot dim lights during driving. A corroding relay, the plastic switching unit, interrupts a single circuit rather than the whole charging output. A sticking thermostat, the coolant flow valve, governs engine temperature and plays no electrical role.
- A technician wants to check the state of charge of a 12-volt battery that has been sitting with the engine off. Which procedure gives the correct reading?
- Bridge the DMM leads across the battery posts, where eighty raw amperes marks full charge
- Watch the CCA dial across the battery posts, where seventy starter amps marks full charge
- Measure the DC voltage across the battery posts, where twelve point six marks full charge
- Sample the AC hertz across the battery posts, where sixty output cycles marks full charge
Correct answer: Measure the DC voltage across the battery posts, where twelve point six marks full charge
The procedure that reports state of charge is to measure the DC voltage across the battery posts, where twelve point six marks full charge, with about 12.4 volts near three quarters and 12.0 volts nearly flat. Bridging meter leads set to amperes straight across the posts creates a dead short through the meter and blows its fuse. A cranking or starter current reading loads the battery and reports its output under strain, not its resting charge. A battery supplies direct current, so an AC or frequency reading has nothing to measure.
- When the ignition key is turned to start, a vehicle produces a single loud click from the starter area but the engine does not crank. Which condition does this symptom MOST commonly indicate?
- A degraded diode or winding, the charging circuit parts
- A shorted coil or terminals, the ignition control parts
- A sticking cable or linkage, the throttle control parts
- A failing solenoid or motor, the cranking circuit parts
Correct answer: A failing solenoid or motor, the cranking circuit parts
A single loud click with no rotation points to a failing solenoid or motor, the cranking circuit parts, because the solenoid plunger pulls in and makes the click while the motor fails to turn the engine, often alongside a discharged battery or high resistance at the cable ends. A degraded diode or winding, the charging circuit parts, governs how the battery is replenished and takes no part in turning the engine over. A shorted coil or terminals, the ignition control parts, would leave the engine turning over without firing rather than silent. A sticking cable or linkage, the throttle control parts, governs airflow once the engine is running.
- To verify alternator output, a technician connects a voltmeter across the battery terminals and starts the engine. Which reading indicates the charging system is working normally?
- Between 13.5 and 14.5 volts, a healthy alternator output with the engine running
- Between 11.5 and 12.5 volts, a discharging battery drain with the engine running
- Between 15.5 and 16.5 volts, a steady overcharge warning with the engine running
- Between 17.5 and 18.5 volts, a collapsed regulator surge with the engine running
Correct answer: Between 13.5 and 14.5 volts, a healthy alternator output with the engine running
A normally working charging system shows between 13.5 and 14.5 volts, a healthy alternator output with the engine running, since the alternator has to sit above the battery resting figure of about 12.6 volts to replace charge and carry the load. A reading between 11.5 and 12.5 volts means the alternator is contributing nothing and the battery alone is running the vehicle. Anything sustained above roughly 15 volts is overcharging, which boils electrolyte and cooks the battery, so both of the higher ranges signal a failed regulator rather than normal operation.
- A circuit is dead and the technician suspects a blown blade fuse. What is the BEST way to confirm whether that fuse is good without removing it?
- Install a vastly larger blade fuse onto the empty holder tabs, keeping the circuit powered
- Touch a test light onto the twin uncovered metallic fuse tabs, keeping the circuit powered
- Rest a resistance meter onto the two active element fuse tabs, keeping the circuit powered
- Spray a foaming cleaner solvent onto the dirty gray fuse tabs, keeping the circuit powered
Correct answer: Touch a test light onto the twin uncovered metallic fuse tabs, keeping the circuit powered
The best in-place check is to touch a test light onto the twin uncovered metallic fuse tabs, keeping the circuit powered: a good fuse lights the lamp on both tabs, while a blown one lights only on the feed side. Installing a vastly larger blade fuse into the holder defeats the circuit protection and can melt wiring or start a fire. A resistance meter must never be used on a live circuit, because applied voltage corrupts the reading and can damage the meter. Cleaning solvent addresses corrosion, which is not what a blown element is.
- A battery's label lists a CCA rating of 650. What does this number describe?
- The amps the battery accepts for continual hours at idle throttle, floating above the charge output level
- The amps the battery yields for sixty minutes at eighty Fahrenheit, peaking above the cranking load lines
- The amps the battery discharges for thirty seconds at zero degrees, remaining above seven point two volts
- The amps the battery retains for lengthy days at room warmth, totalling above the listed capacity ratings
Correct answer: The amps the battery discharges for thirty seconds at zero degrees, remaining above seven point two volts
Cold cranking amps is the amps the battery discharges for thirty seconds at zero degrees, remaining above seven point two volts, so 650 CCA describes cold weather starting power rather than anything else on the label. The current a battery accepts from a charger is a charging specification set by the alternator or charger, not by the battery label. A one hour delivery figure at eighty Fahrenheit is closer to reserve capacity, which is quoted in minutes. Stored energy at room temperature is amp hours, a capacity number and not a cranking number.
- A vehicle will not start. The dome light and headlights are bright, the radio works normally, but turning the key to start produces no cranking and no click. Which component is the MOST likely cause?
- The blower or heating motors, since the passenger fan shares cranking circuits
- The battery or ground strap, since the fading charge barely reaches dashboards
- The alternator or drive belt, since the charging output cranks stopped engines
- The starter or control circuit, since the bright lamps signal working voltages
Correct answer: The starter or control circuit, since the bright lamps signal working voltages
The likeliest cause is the starter or control circuit, since the bright lamps signal working voltages, which rules out a discharged battery and leaves the solenoid, the start relay, or the ignition switch feed as the break. The blower and heating motors sit on their own supply and have no role in cranking, so they share no cranking circuits. A battery or ground strap weak enough to stop the starter could not hold the headlights bright and the radio playing. The alternator and its drive belt only replace charge once the engine is turning, so neither is needed to crank.
- A technician suspects high resistance in the positive battery cable. To perform a voltage drop test on that cable, what should the technician do?
- Position the voltmeter leads at the cable ends, reading the drop during engine cranking
- Press the digital leads at the cable terminals, reading the drops during silent parking
- Clip the ohmmeter leads at the loose cable, reading the resistance during bench testing
- Hold the meter leads at the cable connectors, reading alternating ripple during key off
Correct answer: Position the voltmeter leads at the cable ends, reading the drop during engine cranking
A voltage drop test means positioning the voltmeter leads at the cable ends, reading the drop during engine cranking, because resistance only reveals itself while current is actually flowing; roughly 0.1 to 0.2 volt is acceptable across a battery cable. Pressing digital probes onto the cable terminals of a parked vehicle reports state of charge and says nothing about the cable. Clipping an ohmmeter to a disconnected cable asks the meter to resolve a few milliohms with no load applied. An alternating ripple reading with the key off measures nothing on a direct current cable.
- A customer's battery goes dead after the car sits unused for several days, yet the battery and charging system both test good. Which condition should the technician investigate?
- A ruptured fuse from a connector or terminal that sits cold with headlamps off
- A parasitic drain from a module or circuitry that remains powered with key off
- A voltage overload from a rotor or regulator that idles warm with ignition off
- A sluggish starter from a shaft or brush that drags harshly with frost outside
Correct answer: A parasitic drain from a module or circuitry that remains powered with key off
The condition to chase is a parasitic drain from a module or circuitry that remains powered with key off, an unwanted current that keeps flowing after shutdown and flattens a good battery over several days; it is found with a milliamp meter in series at the negative post. A ruptured fuse from a connector or terminal opens its circuit, and an open circuit cannot drain anything. A voltage overload from a rotor or regulator is impossible while parked, since the alternator produces nothing with the engine stopped. A sluggish starter draws heavily only during cranking, not while the vehicle sits.
- A technician sets up a new ring and pinion in a rear axle and finds the gear tooth contact pattern is centered on the tooth face but too close to the small (toe) end of the gear teeth. To move the pattern toward the larger (heel) end, the technician should:
- Set the ring gear and pinion closer together, reducing the backlash clearance
- Set the ring gear and pinion noticeably inboard, thinning the mounting washer
- Set the ring gear and pinion farther apart, increasing the backlash clearance
- Set the ring gear and pinion tighter throughout, raising the bearing preloads
Correct answer: Set the ring gear and pinion farther apart, increasing the backlash clearance
To walk a toe biased pattern toward the heel the technician should set the ring gear and pinion farther apart, increasing the backlash clearance, because backlash is what moves the contact lengthwise along the tooth. Setting them closer together, reducing the backlash clearance, drives the pattern the wrong way and deepens the toe bias. Thinning the mounting washer alters pinion depth, which raises or lowers the pattern on the tooth profile instead of shifting it toe to heel. Raising the bearing preloads changes rolling drag and bearing life and relocates nothing.
- A customer's vehicle uses electric power steering (EPS) instead of a hydraulic system. Which statement BEST describes how an EPS system provides steering assist?
- An engine driven pump, pushed by hydraulic pressure, adds assist at the steering box
- An inlet vacuum bellows, drawn by plenum suction, adds assist at the steering column
- An accumulator gas globe, charged by stored force, adds assist at the steering valve
- An electric motor, guided by module sensor inputs, adds assist at the steering shaft
Correct answer: An electric motor, guided by module sensor inputs, adds assist at the steering shaft
Electric power steering works because an electric motor, guided by module sensor inputs, adds assist at the steering shaft, with the module reading driver torque and steering angle and tailoring the help to road speed. An engine driven pump pushed by hydraulic pressure is the arrangement that EPS replaces, and it carries no sensors. An inlet vacuum bellows drawn by plenum suction describes a brake booster and has never been used to steer. An accumulator gas globe belongs to hydropneumatic suspension and some hybrid brake systems rather than to a steering gear.
- A technician is replacing the inner tie rod ends on a rack-and-pinion steering system. The inner tie rod connects to which component?
- The machined tip of the steering rack assembly
- The outboard ball of the steering rack knuckle
- The pitman lever of the steering rack gearcase
- The control joint of the steering rack bracket
Correct answer: The machined tip of the steering rack assembly
An inner tie rod threads or pins onto the machined tip of the steering rack assembly, so rack travel is passed straight into the tie rod as the pinion turns. The outboard ball at the knuckle is where the outer tie rod end attaches, one joint further outboard. A pitman lever belongs to a recirculating ball steering box and does not exist on a rack and pinion vehicle at all. The control joint at the suspension bracket is a load carrying ball joint, which a tie rod never bolts to.
- During an alignment, the steering axis inclination (SAI) reads correctly but camber is out of specification and cannot be adjusted into range. A difference between SAI and included angle from side to side MOST often indicates what?
- A sagged steering strut, the camber carrying turret
- A bent steering knuckle, the camber holding spindle
- A worn steering bearing, the camber retaining plate
- A moved steering cradle, the camber shifting mounts
Correct answer: A bent steering knuckle, the camber holding spindle
A side to side difference in included angle while SAI itself reads correctly points to a bent steering knuckle, the camber holding spindle, because SAI is machined into that casting and included angle is simply SAI plus camber. A sagged steering strut, the camber carrying turret, drops ride height and leaves the machined angles paired as built. A worn steering bearing, the camber retaining plate, adds play at the top of the strut and shows as noise and wander rather than a fixed angle error. A moved steering cradle, the camber shifting mounts, swings camber and SAI together, so SAI would read out of range rather than correct.
- A vehicle equipped with a torsion-bar front suspension sits too low in the front. Which procedure correctly raises the ride height?
- Inflate the front tires firmly, lifting the sagging torsion suspension
- Install the stiffer shock absorbers, pushing the torsion bar downwards
- Tighten the torsion adjustment bolts, twisting the bar preload upwards
- Unfasten the strut mounting nuts, letting the torsion springs lengthen
Correct answer: Tighten the torsion adjustment bolts, twisting the bar preload upwards
Ride height is restored by tightening the torsion adjustment bolts, twisting the bar preload upwards, because the torsion bar is the spring and winding more twist into it raises that corner. Inflating the front tires firmly changes rolling radius by a few millimeters and does nothing to spring rate or trim height. Stiffer shock absorbers only limit travel; a damper carries no static weight, so it cannot hold the front up. Unfastening the strut mounting nuts releases nothing useful and leaves a dangerous, unsecured suspension, and a torsion bar vehicle has no strut spring to extend.
- A vehicle with electronically controlled air suspension shows a warning light and one corner is sagging. The air compressor runs but cannot maintain pressure at that corner. What is the MOST likely cause?
- A stretched outboard tie rod, the steering corner coupling
- A wobbling wheel assembly, the rotating road contact patch
- A severe positive caster, the spindle tilted angle setting
- A leaking bellows spring, the corner supporting rubber bag
Correct answer: A leaking bellows spring, the corner supporting rubber bag
When the compressor keeps running yet one corner stays down, the likeliest fault is a leaking bellows spring, the corner supporting rubber bag, or the line feeding it, because that bag is what holds the vehicle up and a leak bleeds it away faster than the pump refills it. A stretched outboard tie rod, the steering corner coupling, changes toe and causes wander, and it carries no load. A wobbling wheel assembly, the rotating road contact patch, produces vibration at speed and no loss of height. A severe positive caster, the spindle tilted angle setting, alters steering feel and cannot make a corner sag.
- A vehicle's left front brake stays partially applied and that wheel is hot, but the caliper, slide pins, and master cylinder all test fine. After driving, opening the bleeder at that caliper releases a spurt of pressure and the wheel then spins freely. Which component is the MOST likely cause?
- A collapsed rubber hose, the flexible lining acting one way
- A trapped air pocket, the spongy cushion giving mushy pedal
- A brimming fluid chamber, the topped tank barring free flow
- A warped rotor face, the uneven surface causing steady beat
Correct answer: A collapsed rubber hose, the flexible lining acting one way
The component that fits every clue is a collapsed rubber hose, the flexible lining acting one way, because a deteriorated inner liner can swell or flap so it passes pressure outward to apply the brake yet blocks the return path, which is exactly why cracking the bleeder frees the wheel. A trapped air pocket, the spongy cushion giving mushy pedal, compresses under the foot and cannot hold a caliper applied. A brimming fluid chamber, the topped tank barring free flow, would drag all four corners through a blocked compensating port, not one wheel alone. A warped rotor face, the uneven surface causing steady beat, produces pulsation and never traps pressure.
- A technician is explaining why a vehicle's hydraulic system limits how much pressure reaches the rear brakes during a hard stop. What is the primary purpose of the proportioning valve's proportioning function?
- To raise the rear pressure during a hard stop, adding traction beyond the axles
- To cap the rear pressure during a hard stop, delaying lockups behind the fronts
- To boost the rear pressure during a hard stop, easing effort inside the booster
- To vent the rear pressure during a hard stop, purging bubbles along the circuit
Correct answer: To cap the rear pressure during a hard stop, delaying lockups behind the fronts
The proportioning function exists to cap the rear pressure during a hard stop, delaying lockups behind the fronts, because weight shifts forward under heavy braking and the lightly loaded rear wheels would otherwise skid first and swing the vehicle around. Raising rear pressure to add traction is the opposite move and would make the rear lock even sooner. Easing pedal effort inside the booster is the job of the vacuum or hydraulic assist, which is a separate device. Purging bubbles along the circuit is bleeding, a manual service task rather than a valve function.
- A vehicle's battery repeatedly discharges, and a technician suspects a failed alternator diode. Which test result would BEST confirm a defective rectifier diode in the alternator?
- A firm DC rise near fourteen volts, measured at the battery posts with the engine running
- A nil DMM resistance near zero ohms, measured at the battery posts with the engine idling
- A climbing AC ripple near one volt, measured at the battery posts with the engine running
- A calm OCV value near twelve volts, measured at the battery posts with the engine sitting
Correct answer: A climbing AC ripple near one volt, measured at the battery posts with the engine running
A defective rectifier diode is confirmed by a climbing AC ripple near one volt, measured at the battery posts with the engine running, since a healthy rectifier leaves only a few tenths of a volt of alternating content and a shorted or open diode lets raw alternating current through. A firm DC rise near fourteen volts is exactly what a good charging system produces, so it confirms nothing is wrong. A near zero resistance reading across the posts would mean a dead short and is no kind of diode test. A calm open circuit value near twelve volts merely reports a charged battery at rest.
- A 12-volt series lighting circuit contains two resistive elements wired in series, one of 2 ohms and one of 4 ohms. Using Ohm's law, what is the current flowing through this circuit?
- Six amperes, the volts divided by smaller component
- Three amperes, the volts divided by biggest element
- Twelve amperes, the volts divided by zero resistors
- Two amperes, the volts divided by summed resistance
Correct answer: Two amperes, the volts divided by summed resistance
Series resistances add, so two ohms plus four ohms gives six ohms, and Ohm's law makes the current twelve volts over six ohms, which is two amperes, the volts divided by summed resistance. Six amperes comes from dividing by the smaller component alone and ignoring the other part of the loop. Three amperes comes from dividing by the biggest element alone, which repeats that mistake at the other end. Twelve amperes treats the circuit as though it opposed nothing at all, which no resistive circuit does.
