- ADAS
- Advanced Driver Assistance Systems — electronic features (ACC, lane-keeping, AEB, blind-spot, parking assist) that use sensors to help the driver.
- ADAS calibration
- Aligning a sensor's aim with the vehicle's true centerline and forward direction so it measures distances and angles accurately. Required whenever a sensor is moved, replaced, or its reference geometry changes.
- Static calibration
- Done with the vehicle stationary in the shop, aimed at OEM targets at exact distances on a level floor under controlled lighting, with a scan tool running the routine.
- Dynamic calibration
- Done by driving the vehicle at a specified speed on well-marked roads while a scan tool runs the routine; the sensor learns from real lane lines, vehicles, and signs.
- Combined calibration
- An OEM procedure requiring a static setup first, then a dynamic drive to finish; common on late-model vehicles. The order is set by the manufacturer.
- Sensor fusion
- Combining inputs from camera, radar, and ultrasonic sensors into one picture of the surroundings. A fault in any one sensor can disable a fused feature.
- Three ADAS sensor types
- Camera (optical — lane lines, signs, objects), radar (radio — distance and speed in any weather), and ultrasonic (sound — close-range parking).
- OEM service procedure
- The manufacturer's exact targets, distances, floor, lighting, scan tool, and static/dynamic sequence for a specific vehicle — the only correct way to calibrate.
- Calibration pre-conditions
- Level floor, correct tire pressures and ride height, stable battery voltage, clean sensor/windshield, OEM targets at exact distances, and correct wheel alignment.
- Why most calibrations fail
- A missed pre-condition (uneven floor, wrong ride height, low voltage, dirty sensor, bad alignment, or mis-set targets), not a bad sensor.
- Ride height and ADAS
- Sensor aim depends on ride height. Extra cargo, low fuel, or wrong tire pressures change it and can fail or skew a calibration.
- Wheel alignment and ADAS
- Sensors are aimed relative to the rear-wheel thrust line, so a four-wheel alignment is usually required before calibrating forward-facing sensors.
- Thrust line
- The direction the rear wheels actually point; ADAS forward sensors are aimed relative to it.
- Battery voltage during calibration
- Must be stable and adequate — low or fluctuating voltage interrupts module communication and aborts the calibration routine.
- Health check (pre/post scan)
- A full-vehicle scan run before and after ADAS service to record existing faults and confirm all systems work after the repair and calibration.
- Where ADAS DTCs are stored
- Often in the radar, camera, or steering-angle module — not just the body controller — so scan all modules.
- Steering-angle sensor
- Reports steering position to the ADAS to predict the vehicle's path. Reset with the wheels straight ahead after alignment, replacement, or a battery disconnect.
- Steering-angle zero-point reset
- A relearn done with the steering wheel exactly straight ahead; a wrong reference makes lane-centering wander or disable itself.
- Composite Vehicle Type 1
- A sample ADAS-equipped vehicle ASE describes in a reference document during the L4 test; many questions are based on it.
- Calibration target
- A printed or 3-D fixture placed at OEM-specified positions that a sensor uses as a known reference during static calibration.
- Level floor requirement
- Static calibration needs a flat, level floor so the targets and sensor share a true reference plane; a sloped floor skews the aim.
- Controlled lighting requirement
- Static camera calibration needs even lighting — glare, shadows, or reflections can cause it to fail.
- Diagnose before condemning
- Most ADAS faults are mechanical or environmental (blocked sensor, misalignment, non-OEM part). Inspect the sensor and mounting before replacing a module.
- Most ADAS faults are physical
- Dirt, ice, misalignment, moisture, or a non-OEM part — not an electronic module failure.
- When recalibration is required
- After windshield or bumper R&R, a sensor replacement or disturbance, a wheel alignment or ride-height change, or collision repair near a sensor.
- Adaptive cruise control (ACC)
- Maintains a set speed and automatically keeps a set following distance, primarily using forward radar (often fused with the camera).
- Automatic emergency braking (AEB)
- Detects an impending front collision and brakes if the driver does not react, fusing radar (distance/speed) with the camera (object ID).
- Forward collision warning (FCW)
- Alerts the driver to an impending front collision; AEB adds automatic braking to the same sensing.
- Lane-keeping assist (LKA)
- A camera-based system that detects lane markings and steers or warns to keep the vehicle in its lane. LDW is the alert-only version.
- Lane departure warning (LDW)
- A camera-based alert when the vehicle drifts out of its lane without a turn signal; the alert-only counterpart to lane-keeping assist.
- Blind-spot detection (BSD)
- Usually radar-based; warns when a vehicle is in the driver's blind spot. Rear cross-traffic alert is related.
- Traffic-sign recognition
- A camera feature that reads speed-limit and other road signs; degraded by a dirty lens, glare, or a non-OEM windshield.
- Surround-view (360°) system
- Stitches images from multiple cameras for a bird's-eye parking view; a black quadrant points to that quadrant's camera or its feed.
- GPS in ADAS
- Some features use GPS and map data to anticipate curves and speed limits; weak reception or an outdated map degrades these predictive features only.
- Driver monitoring system
- A cabin camera or sensor that watches for drowsy or distracted driving; part of the broad ADAS family the L4 covers.
- Head-up display (HUD)
- Projects information onto the windshield in the driver's view; among the systems an L4 technician services.
- Why a fraction of a degree matters
- Small aiming errors throw a sensor's view off by feet at a distance, so an uncalibrated sensor can react at the wrong place or time.
- Post-repair road test
- After calibration, drive the vehicle to confirm features perform and no codes return — part of verifying an ADAS repair.
- Pulling to one side after windshield R&R
- Most likely a misaligned/uncalibrated forward camera, not a steering fault — recalibrate the camera.
- Tire condition and ADAS
- Worn or improperly inflated tires change ride height and aim; inspect tires and pressures before calibrating.
- Liability of ADAS repair
- ADAS is safety-critical; document the OEM procedure and post-repair verification to confirm the system was returned to spec.
- Aftermarket part risk (general)
- Non-OEM glass, bumpers, emblems, wheels, or sensors can prevent calibration, block a signal, or shift aim even if a self-test passes.
- Scan tool role in calibration
- Initiates the routine, tells the sensor what it should be seeing (static) or runs the learn routine (dynamic), and reports completion or faults.
- Initialization vs. calibration
- Initialization/relearn teaches a sensor a new zero or position (e.g., steering angle, ultrasonic); calibration aims a sensor to OEM targets/geometry.
- Centerline reference
- Calibration aligns sensors to the vehicle's geometric centerline and thrust line so their view matches the true direction of travel.
- Preload/stress check after collision
- Verifies no residual stress at the sensor mounting points is throwing off sensor alignment after a repair.
- Notch filter (radar)
- An electronic filter used with radar to reduce interference from other vehicle systems.
- Health of lane markings
- Faded, missing, or wet lane markings on the road or track are a frequent cause of failed dynamic calibration.
- Why scan ALL modules
- ADAS functions span several modules; a fault in one (radar, camera, steering angle) can disable a feature controlled by another.
- Units of measurement in setup
- ADAS setup may require converting between standard and metric (tape measure, laser, level, plumb bob) to place targets correctly.
- Forward-facing camera
- The optical sensor (usually windshield-mounted) that reads lane lines, signs, vehicles, and pedestrians for lane-keeping, AEB, and sign recognition.
- Where the forward camera mounts
- To the windshield behind the rearview mirror, so the glass is part of its optical path.
- Why windshield R&R needs camera calibration
- Replacing the glass moves the camera and changes the optical path, so it must relearn where it is aiming.
- Non-OEM windshield risk
- Different thickness, tint, or optical clarity can prevent camera calibration or degrade its view.
- Clean the windshield first
- A dirty, fogged, or filmed windshield (inside and out) degrades the camera and can fail calibration — clean before condemning the module.
- Camera blinding conditions
- Sun glare, heavy rain, snow, fog, darkness, dirt, tint, and stickers in front of the lens all degrade an optical camera.
- Camera identifies, radar measures
- The camera tells WHAT an object is (car, sign, lane); radar measures HOW FAR and HOW FAST — they fuse for ACC and AEB.
- Lane markings and the camera
- Faded or missing lane lines stop a camera-based lane-keep from tracking, especially on curves, and fail dynamic calibration.
- Static camera calibration needs
- OEM targets at exact distances, a level floor, and even, controlled lighting with no glare or reflections.
- Dynamic camera calibration needs
- Clear, well-marked roads driven at the specified speed range so the camera learns real lane lines and signs.
- Camera bracket/mirror replacement
- Disturbs the camera and requires recalibration, just like a windshield replacement.
- Black quadrant on surround view
- Inspect the specific camera feeding that quadrant (or its wiring) first.
- Camera and adaptive headlights
- A camera-based adaptive headlight system aims light using the camera; a dirty lens or misaim degrades it (misaligned front wheels do not directly cause it).
- Hydrophobic coating on the lens
- A water-shedding coating; when it degrades, the camera can give intermittent function in heavy rain.
- Aftermarket front camera install
- Mount it at the OEM-recommended height and angle, then calibrate — wrong placement guarantees poor performance.
- Suspension geometry change and the camera
- Can misalign the camera's view without any physical damage to the camera — recalibrate after suspension/ride-height changes.
- Camera vs. radar weather
- The camera struggles in fog, glare, and dark; radar still works — which is why systems fuse them.
- Pedestrian detection
- A camera (often fused with radar) identifies pedestrians for warnings and AEB; a degraded lens reduces reliability.
- Traffic-sign recognition faults
- Caused by a dirty lens, glare, a non-OEM windshield, or obscured/faded signs — not by mechanical engine faults.
- Camera well-lit, level surface
- During calibration the vehicle must sit on a level surface in a well-lit area for the camera to reference correctly.
- Windshield optical clarity
- Distortion, waviness, or heavy tint in the camera's viewing zone degrades recognition and can block calibration.
- Lane-keep wanders on curves
- Often improper camera alignment/calibration — recheck the camera aim and calibration.
- Camera-based ACC support
- Some ACC fuses the camera for object classification with radar for range; a camera fault can degrade ACC behavior.
- Recalibrate after camera replacement
- A new camera does not know its aim — it must be calibrated to OEM targets/geometry before the feature is trusted.
- Internal vs. external windshield cleanliness
- Both sides matter — a film on the inside of the glass blinds the camera as much as dirt outside.
- Camera mounting angle
- Must match OEM spec; an off-angle camera (from a bad bracket or windshield) aims its view wrong and fails calibration.
- Why cameras need lane lines to learn
- Dynamic calibration relies on the camera seeing real markings; on an unmarked or worn road it cannot complete.
- Cracked windshield over the camera
- A crack or chip in the camera's view distorts the image and can prevent calibration — use OEM glass and a clear viewing zone.
- Camera and traffic-light/sign glare
- Bright backlighting or glare can wash out the image; this is an optical limitation, not a module fault.
- Multiple cameras in modern vehicles
- Front (windshield), rear, and side/mirror cameras feed different features; identify which camera drives the failing feature.
- RADAR
- Radio Detection and Ranging — emits radio waves and reads reflections to find an object's distance and closing speed, working in rain, fog, and dark.
- How radar finds distance and speed
- Time delay of the reflection gives distance; the Doppler frequency shift gives closing speed.
- Where radar mounts
- Behind the grille or bumper (front) and in the rear corners (blind-spot/cross-traffic).
- Radar drives which features
- Adaptive cruise control, the braking half of AEB, blind-spot detection, and rear cross-traffic alert.
- Radar all-weather advantage
- Radio waves work in rain, fog, and darkness — which is why radar is the backbone of ACC and AEB.
- Dirty/iced radar face
- A dirty, iced, or snow-covered sensor face causes ACC/AEB/BSD to drop out or fail to detect.
- Misaligned or dented bumper
- Aims the radar beam off-target, causing false or missed alerts — a common physical fault.
- Non-OEM bumper cover and radar
- Can block or deflect the radar signal; verify an OEM, undamaged cover in the beam path.
- Foil-backed/metallic emblem
- An emblem in the radar beam path can block or deflect the signal.
- Moisture in the radar housing
- Causes sporadic malfunctions, often only during heavy rain, with no stored DTC.
- Weather-dependent fault, no DTC
- Usually moisture or a blocked/dirty sensor — a physical condition that only appears when wet, not a failed module.
- Radar mounting and impact
- Even a minor impact can loosen or misalign the sensor and aim the beam off-target.
- Bumper R&R requires radar recalibration
- Because radar sits behind the bumper, any bumper R&R or collision repair near it usually requires recalibration.
- Radar in ACC
- Measures the distance and closing speed of the vehicle ahead so ACC keeps a set following gap.
- Radar in AEB
- Provides the distance and closing-speed data that triggers automatic braking when a collision is imminent.
- AEB brakes less than expected
- Check related systems such as the ABS that actually applies the braking, plus radar aim and condition.
- Blind-spot radar in the rear corners
- Corner radars watch the adjacent lanes; non-OEM wheels or modifications can confuse detection.
- Rear cross-traffic alert
- Uses rear-corner radar to warn of approaching vehicles when backing out; intermittent failure points to sensor mounting/wiring.
- Radar sensor cleanliness with no DTC
- If BSD is dead but no codes are set, suspect a dirty or blocked sensor surface first.
- Non-OEM wheels and radar
- Can affect blind-spot detection by altering the vehicle's geometry or reflections.
- Collision mitigation activates randomly
- Often the radar sensor's condition or positioning (dirty, misaimed, or loose) — inspect and clean before replacing.
- Radar beam alignment is critical
- The mounting angle aims the beam; it must be set and verified to OEM spec on a level surface.
- Inspect radar before condemning
- Clean the sensor and verify an OEM, undamaged bumper before replacing a radar module.
- LED headlight upgrade and radar
- Aftermarket lighting does not power radar; it is not the cause when ACC can't maintain speed (a distractor on the exam).
- Radar vs. camera roles
- Radar measures range and speed in any weather; the camera classifies objects and reads lanes/signs — they complement each other.
- Snow/mud packing on the sensor
- Blocks the radar and disables forward features until cleared.
- Loose radar wiring/connector
- Causes intermittent operation of the radar-fed feature; check mounting and harness.
- Radar calibration after collision repair
- Required whenever repair work disturbs the sensor or its mounting bracket near the bumper.
- Notch filter purpose
- Reduces interference from other vehicle systems so the radar reads true returns.
- Cross-traffic only in reverse
- By design, rear cross-traffic alert is meant to operate when backing — not a fault.
- ACC can't hold set speed/gap
- Inspect the radar sensor's condition and positioning (dirty, misaimed, blocked) rather than unrelated electrical upgrades.
- Radar field of view
- A focused forward cone; objects outside it (or blocked by a non-OEM part) are not detected.
- Ultrasonic sensor
- A short-range bumper-mounted sensor that emits high-frequency sound pulses and times the echo to measure distance to close objects (parking assist). Also called sonar.
- How ultrasonic sensing works
- Emits sound pulses and measures time-of-flight (echo time) to nearby objects; useful range is only a few meters.
- Where ultrasonic sensors mount
- In the front and rear bumpers, at precise angles.
- Ultrasonic features
- Parking assist beeps, self-parking, and some rear cross-traffic and low-speed maneuvering aids.
- Ultrasonic environmental limits
- Affected by dirt, ice, snow, heavy rain, and loud ambient noise at a frequency similar to the sensor's.
- Dirty ultrasonic sensor face
- A dirty, iced, or snow-covered sensor causes parking assist to false-alert or fail to detect — clean and retest first.
- Bumper R&R and ultrasonic relearn
- Replacing or repairing the bumper moves the sensors and changes how sound passes through the cover, so the system must be reinitialized.
- Excess paint over the sensor
- Too-thick paint muffles the signal and causes false or missing detections.
- Ultrasonic reinitialization (learn)
- A relearn procedure so the system reads the sensors' new positions and paint thickness correctly after bumper work.
- Calibrate ultrasonic on level surface
- An out-of-level vehicle can prevent ultrasonic calibration/initialization from completing.
- One side stops detecting
- Check the integrity and routing of the wiring harness on that side of the bumper.
- Misaligned bumper and ultrasonic
- A bumper out of position changes the sensor angles, giving incorrect distance or uneven coverage.
- Loud ambient noise
- Noise near the sensor's operating frequency reduces or disrupts its detection range.
- Water in wet conditions
- Water on the sensor can temporarily change its acoustic properties, causing intermittent operation in the rain.
- Non-OEM ultrasonic sensors
- May not match the system's frequency or sensitivity, leading to poor or inconsistent detection.
- Self-parking after sensor replacement
- Requires system initialization and the learning process so the new sensor reports correctly.
- Ultrasonic vs. radar range
- Ultrasonic is very short-range (parking); radar reaches far ahead (cruise/collision) — different jobs.
- Ultrasonic blind-spot detection
- Some BSD uses ultrasonic sensors; a misaligned bumper housing them causes incorrect detection.
- Reprogram/recalibrate trigger
- After replacing or repairing a bumper where the sensors are housed, recalibrate/relearn the ultrasonic system.
- Cleanliness check first
- When parking assist is not working, check the cleanliness of the sensor faces before deeper diagnosis.
- Acoustic path through the bumper
- Sound must pass cleanly through the cover; thick paint, body filler, or debris over the sensor degrade it.
- Sensor face damage
- Cracks or physical damage to a sensor change its sound pattern and cause false or missed detections.
- Why ultrasonic is close-range only
- Sound attenuates quickly, so the sensors are useful only within a few meters — fine for parking, not for highway speed.
- Connector corrosion
- Corroded or loose connectors cause intermittent ultrasonic sensor operation, especially after wet exposure.
- Initialization vs. calibration (ultrasonic)
- Ultrasonic systems are typically initialized/relearned to their positions rather than aimed at targets like a camera or radar.
- Snow/ice packed in the bumper
- Blocks ultrasonic sensors and disables parking assist until cleared.
- Repaint and sensor performance
- Repainting the bumper without controlling paint thickness over the sensor degrades detection — follow OEM paint specs.
- Ultrasonic in self-parking
- Measures distances to curbs and cars to guide the automated steering; misaimed or dirty sensors cause poor parking.
- Verify with a known object
- Test ultrasonic detection against a known object at a measured distance to confirm proper operation after service.
- Ambient temperature effect
- Extreme temperature can slightly affect the speed of sound and sensor readings; OEM systems compensate, but a fault can exaggerate it.
- Verify the customer concern first
- Confirm and reproduce the complaint (false alert, won't enable, warning light) and get repair history before testing.
- Repair history matters in ADAS
- Ask whether the windshield, bumper, or suspension was recently serviced — it often points to the missed calibration.
- False alert diagnosis
- A system alerting with nothing there often means a misaimed, dirty, or uncalibrated sensor — inspect before replacing.
- System won't enable
- A feature that refuses to turn on may have an unmet condition (speed, weather, blocked sensor) or a stored fault disabling it.
- Warning light vs. feature loss
- A lit ADAS warning means a stored fault; scan all modules to find which sensor/module set the code.
- Calibration completes but aims wrong
- Wrong targets, an unlevel floor, or bad alignment can finish the routine yet leave a dangerous aiming error.
- Documentation of OEM procedure
- Record the procedure used and the post-repair test to prove the ADAS was returned to spec (liability).
- Scan tool communication
- A stable connection and adequate voltage are required; dropouts abort calibration mid-routine.
- Pre-scan purpose
- Captures faults that existed before your work so you don't get blamed for them and know the starting state.
- Post-scan purpose
- Confirms the repair cleared the fault and that calibration left every module operating correctly.
- Sensor mounting bracket
- Holds the sensor at the OEM angle; a bent or replaced bracket changes aim and requires recalibration.
- Level and laser tools in setup
- Used to place targets square and level to the vehicle centerline for accurate static calibration.
- Plumb bob / string in setup
- Helps locate the vehicle centerline and target positions precisely during static calibration.
- Centerline and target placement
- Targets are positioned relative to the vehicle's true centerline; an error here aims the sensor off.
- Tire pressure before calibration
- Correct, even pressures keep ride height true; uneven pressures tilt the vehicle and skew aim.
- Fuel level and cargo
- Low fuel or heavy cargo changes ride height; set the vehicle to the OEM-specified condition before calibrating.
- Aftermarket accessories
- Bull bars, light bars, or trailer hitches can block or reflect sensors — verify the beam path is clear and OEM.
- Software/firmware updates
- Some ADAS faults require a control-module software update before or after calibration per OEM bulletins.
- Module replacement and programming
- A replaced ADAS module often needs programming/configuration plus calibration before the feature works.
- Why pre-conditions are tested on the exam
- ASE composite-vehicle questions check whether you can spot the missing condition blocking a calibration.
- Verify after every ADAS repair
- Always confirm pre-conditions, run calibration, then road-test — skipping verification is a common error.
- Reset after battery disconnect
- A battery disconnect can require relearns (steering angle, sensors) before some ADAS features operate normally.
- Camera height and angle
- An aftermarket or replaced camera must sit at OEM height and angle, then be calibrated, or it sees wrong.
- Windshield ceramic frit / bracket
- The camera bracket bonds to a specific windshield area; a non-OEM glass without the correct bracket zone fails.
- Heated windshield element
- Lines or coatings near the camera zone can interfere; OEM glass keeps the camera's viewing area clear.
- Rain/light sensor near the camera
- Often shares the windshield mount; disturbing the module can affect both the camera and these sensors.
- Camera image distortion
- Waviness or aftermarket tint in the viewing zone distorts the image and degrades recognition.
- Calibration distance to target
- Camera static calibration uses OEM-specified target distances; the wrong distance fails or mis-aims it.
- Camera dynamic speed window
- Dynamic camera calibration must be driven within the OEM speed range on marked roads to complete.
- Lane-keep false activation
- A misaimed camera or worn lane lines can cause unwanted steering inputs or warnings.
- Camera condensation/fog
- Internal fogging of the camera area blinds it intermittently; address the moisture source.
- Color and contrast recognition
- Cameras rely on contrast to read lanes and signs; low light or glare reduces reliability.
- Multiple-camera calibration order
- Surround-view systems may require calibrating each camera and then the stitched view per OEM steps.
- Verify camera view is unobstructed
- Stickers, toll tags, or dash items in the camera's field block recognition.
- Radar bracket alignment
- The radar's bracket sets its angle; verify it is OEM and undamaged before and after calibration.
- Front radar location options
- Behind the grille emblem, lower bumper, or center — know where the specific vehicle's radar lives.
- Radar self-alignment vs. calibration
- Some radars auto-align while driving; others require a static target — follow the OEM procedure.
- Radar blockage DTC
- A 'sensor blockage' code usually means dirt, ice, or an obstruction — physically inspect and clean first.
- Plastic vs. metal in the beam
- Radar sees through OEM plastic covers but is blocked by metal/foil — non-OEM materials can defeat it.
- Adaptive cruise distance settings
- Driver-selectable gaps change following distance; not a fault if behavior matches the setting.
- Radar and tunnel/overpass
- Stationary metal structures can cause brief false readings; persistent issues indicate a sensor problem.
- Corner radar coverage
- Rear-corner radars cover adjacent lanes; a blocked or misaimed corner radar misses vehicles.
- Radar fascia repaint thickness
- Excess paint/filler over the radar area can attenuate the signal — follow OEM refinish limits.
- Radar after minor fender-bender
- Even with no visible damage, recalibrate front/corner radar after impacts near its mounting.
- Doppler shift concept
- The frequency change of the reflected wave reveals whether an object is closing or moving away, and how fast.
- Radar power/ground check
- Intermittent radar faults can stem from a poor power or ground connection — verify the circuit, not just the sensor.
- Number of bumper sensors
- Vehicles use several ultrasonic sensors per bumper for overlapping coverage; one bad sensor leaves a gap.
- Audible parking-assist tones
- Tone frequency rises as an object nears; no change or constant tone signals a sensor or wiring fault.
- Ultrasonic sensor color-matching
- Sensors are often painted to match; technique and thickness must stay within OEM limits to keep them working.
- Ultrasonic self-test on startup
- Many systems chirp/click at key-on as a self-test; a missing sensor in the test points to a fault.
- Cross-talk between sensors
- Improperly positioned or non-OEM sensors can interfere with each other, causing erratic readings.
- Ultrasonic in cold weather
- Ice or packed snow over the sensor disables it; clear the face before assuming a sensor failure.
- Mounting clip/retainer
- A loose retainer lets a sensor sit at the wrong angle, skewing detection — reseat to OEM position.
- Bumper filler over sensor
- Body filler over or around a sensor changes the acoustic path and degrades detection.
- Reverse vs. forward sensors
- Front and rear ultrasonic sets serve different maneuvers; diagnose the set tied to the failing feature.
- Confirm relearn completed
- After bumper work, verify the initialization/relearn finished and the system detects a known object correctly.
- Ultrasonic detection cone
- Each sensor has a limited detection cone; objects outside it (low curbs, thin poles) may not register.
- Wiring routing after bumper R&R
- Re-route and secure the harness exactly as OEM; a pinched or mis-routed wire causes one side to fail.
