1.
ASE L2: General Inspection and Diagnosis
When diagnosing an electronic diesel fuel system, the appearance of metal shavings in the fuel filter housing suggests:
1 out of 55
2.
ASE L2: General Inspection and Diagnosis
A technician is diagnosing an electronically controlled diesel engine that is running rough. The ECM has logged low voltage for multiple glow plugs. What could cause this issue in all affected circuits simultaneously?
2 out of 55
3.
ASE L2: General Inspection and Diagnosis
When diagnosing a common rail diesel engine that exhibits poor performance and excessive smoke, which of the following is LEAST likely to be checked initially?
3 out of 55
4.
ASE L2: General Inspection and Diagnosis
During the initial inspection of a diesel engine, the technician notes that the engine oil level is significantly overfull. This could be an indication of:
4 out of 55
5.
ASE L2: General Inspection and Diagnosis
A diesel engine's diagnostic scan reveals a DTC for low rail pressure during cranking. What should be checked FIRST?
5 out of 55
6.
ASE L2: General Inspection and Diagnosis
If a diesel engine is experiencing fluctuating oil pressure readings at all engine speeds, what is the MOST likely cause?
6 out of 55
7.
ASE L2: Electronic Engine Controls Diagnosis
When diagnosing an electronically controlled diesel engine that has a delayed start condition, a technician notes that the ICP (Injection Control Pressure) is lower than specified during cranking. What is the LEAST likely cause?
7 out of 55
8.
ASE L2: Electronic Engine Controls Diagnosis
In a common rail diesel injection system, the high-pressure pump is not achieving desired pressure. A DTC for low rail pressure is present. What is the MOST likely cause?
8 out of 55
9.
ASE L2: Electronic Engine Controls Diagnosis
A technician is diagnosing an intermittent stalling issue on a diesel engine. The engine stalls when hot but restarts after cooling down. The stalling is accompanied by loss of RPM signal. What is the most likely culprit?
9 out of 55
10.
ASE L2: Electronic Engine Controls Diagnosis
When troubleshooting an active DTC for "Variable Geometry Turbocharger (VGT) Control Circuit Low," what should a technician examine FIRST?
10 out of 55
11.
ASE L2: Electronic Engine Controls Diagnosis
A technician observes erratic behavior of the fuel gauge and the temperature gauge on a diesel engine vehicle. No relevant DTCs are stored. What is the most likely cause?
11 out of 55
12.
ASE L2: Electronic Engine Controls Diagnosis
An electronically controlled diesel engine is not responding to throttle input. A DTC indicates a fault in the throttle position sensor circuit. What should be checked FIRST?
12 out of 55
13.
ASE L2: Electronic Engine Controls Diagnosis
What diagnostic test should be performed FIRST when a diesel engine has low power and a DTC for "Fuel Pressure - Below Minimum Threshold"?
13 out of 55
14.
ASE L2: Electronic Engine Controls Diagnosis
During the cold start of a diesel engine, excessive white smoke is observed. A DTC for low compression in one cylinder is stored. What is the most likely cause of this condition?
14 out of 55
15.
ASE L2: Electronic Engine Controls Diagnosis
The Check Engine Light of a diesel engine vehicle comes on, and the vehicle enters limp mode. The DTC indicates "Low Voltage at Fuel Quantity Actuator." What is the FIRST step in troubleshooting this issue?
15 out of 55
16.
ASE L2: Electronic Engine Controls Diagnosis
The ECM of a common rail diesel engine reduces power output, and a DTC for "Fuel Temperature - High" is recorded. What is the FIRST component to check?
16 out of 55
17.
ASE L2: Electronic Engine Controls Diagnosis
A diesel engine's turbocharger is not providing enough boost according to the ECM data. No DTCs are present. Which of the following is the most likely cause?
17 out of 55
18.
ASE L2: Electronic Engine Controls Diagnosis
A diesel engine is producing less power and more noise than usual. The ECM has stored a DTC for "Intake Manifold Pressure - High." What should be the technician's first step in diagnosing this issue?
18 out of 55
19.
ASE L2: Electronic Engine Controls Diagnosis
A diesel engine vehicle has been reported to lose power intermittently. A DTC for "MAP Sensor Voltage High" is found. After replacing the MAP sensor, the problem persists. What is the NEXT best step to take?
19 out of 55
20.
ASE L2: Electronic Engine Controls Diagnosis
What is the most common cause for a diesel engine's ECM to log a DTC for "EGR Flow Insufficient" when the EGR valve itself tests good?
20 out of 55
21.
ASE L2: Electronic Engine Controls Diagnosis
A diesel engine is reporting a DTC for the exhaust gas recirculation (EGR) system performance. There are no other codes related to airflow or temperature sensors. What should be checked FIRST to diagnose this DTC?
21 out of 55
22.
ASE L2: Electronic Engine Controls Diagnosis
A technician finds that a diesel engine has a rough idle and a DTC for an injector circuit fault. What should the technician inspect FIRST?
22 out of 55
23.
ASE L2: Electronic Engine Controls Diagnosis
When diagnosing a DTC related to "Intake Throttle Control Circuit Performance," which of the following diagnostic tests should be performed first?
23 out of 55
24.
ASE L2: Electronic Engine Controls Diagnosis
A technician observes that a diesel engine's start-up is taking longer than normal. There are no DTCs present. What is a potential cause for this symptom?
24 out of 55
25.
ASE L2: Electronic Engine Controls Diagnosis
A diesel engine with common rail injection experiences inconsistent acceleration and a DTC for "Injection Timing Error." What is the FIRST step in diagnosing this problem?
25 out of 55
26.
ASE L2: Electronic Engine Controls Diagnosis
During the diagnosis of the electronic control system of a diesel engine, a technician finds a DTC for low voltage to the intake air heater circuit. What is the most likely cause?
26 out of 55
27.
ASE L2: Air Induction Systems Diagnosis
A diesel engine is experiencing intermittent surging under load. The technician suspects an issue with the air induction system. Which of the following should be checked FIRST?
27 out of 55
28.
ASE L2: Air Induction Systems Diagnosis
While troubleshooting a diesel engine with erratic power delivery, a technician discovers that the engine's boost pressure varies significantly under constant load conditions. There are no visible leaks or damage to the turbocharger system. What should the technician inspect next?
28 out of 55
29.
ASE L2: Air Induction Systems Diagnosis
A technician finds oil in the intake manifold of a diesel engine. There are no performance complaints or codes. What is the most likely source of the oil?
29 out of 55
30.
ASE L2: Air Induction Systems Diagnosis
During a road test, a technician observes a lack of power and audible noise from the front of a diesel engine. The turbocharger appears to be functioning properly. What is the most likely cause?
30 out of 55
31.
ASE L2: Air Induction Systems Diagnosis
A diesel engine is not achieving the desired boost pressure. The turbocharger and its control systems are functioning correctly. What should the technician inspect next?
31 out of 55
32.
ASE L2: Air Induction Systems Diagnosis
A diesel engine experiences low power and the turbocharger is suspected. During inspection, the variable geometry turbocharger (VGT) actuator moves freely when commanded with a scan tool, but the problem persists. What is the NEXT best step to diagnose this issue?
32 out of 55
33.
ASE L2: Air Induction Systems Diagnosis
When diagnosing an air induction system of a diesel engine, a technician notes that the intake air heater does not operate. All fuses and relays are functional. What is the most likely cause?
33 out of 55
34.
ASE L2: Air Induction Systems Diagnosis
A diesel engine's air filter service indicator has triggered, but upon inspection, the air filter appears clean and undamaged. What could cause this premature indication?
34 out of 55
35.
ASE L2: Fuel Systems Diagnosis
A technician finds that a diesel engine with common-rail injection starts hard and runs roughly when cold but improves when warm. The likely cause is:
35 out of 55
36.
ASE L2: Fuel Systems Diagnosis
After replacing the injectors on a diesel engine, a technician notes a fluctuation in idle speed and performance. Injector adaptation has been performed. What should be checked NEXT?
36 out of 55
37.
ASE L2: Fuel Systems Diagnosis
A diesel engine is producing excessive noise and vibration. The technician has verified that the fuel quality is good and the injectors are operating correctly. What should be checked NEXT?
37 out of 55
38.
ASE L2: Fuel Systems Diagnosis
A diesel engine is experiencing excessive white smoke at startup which clears after warming up. The smoke is primarily due to:
38 out of 55
39.
ASE L2: Fuel Systems Diagnosis
A technician is diagnosing an electronically controlled diesel fuel system that has a no-start condition. The engine cranks normally. What should the technician check FIRST?
39 out of 55
40.
ASE L2: Fuel Systems Diagnosis
A diesel engine's fuel system has been contaminated with gasoline. After flushing the system and replacing the fuel, the engine runs but with reduced power and excessive smoke. What is the most likely cause?
40 out of 55
41.
ASE L2: Fuel Systems Diagnosis
What could cause a diesel engine equipped with a high-pressure common rail fuel system to display a loss of power and an increased level of noise?
41 out of 55
42.
ASE L2: Fuel Systems Diagnosis
A diesel engine with a unit injector system has a rough idle and a knock. Which of the following could be the cause?
42 out of 55
43.
ASE L2: Fuel Systems Diagnosis
During the diagnosis of a diesel engine, the technician finds metal shavings in the fuel filter. What is the MOST likely source of these shavings?
43 out of 55
44.
ASE L2: Fuel Systems Diagnosis
During a cylinder cutout test on a diesel engine, the technician observes no change in engine running quality when one cylinder is cut out. What is the MOST likely cause?
44 out of 55
45.
ASE L2: Emissions Systems Diagnosis
A diesel engine equipped with an SCR (Selective Catalytic Reduction) system consistently has high NOx emissions under load. The DEF "Diesel Exhaust Fluid" quality is confirmed to be within specification. What should be checked next?
45 out of 55
46.
ASE L2: Emissions Systems Diagnosis
A technician is unable to perform a stationary regeneration on a diesel particulate filter despite multiple attempts and no diagnostic trouble codes present. What is the most likely cause?
46 out of 55
47.
ASE L2: Emissions Systems Diagnosis
A technician is diagnosing a diesel engine that has passed all NOx reduction tests but fails for HC (Hydrocarbon) emissions. What is the most likely cause?
47 out of 55
48.
ASE L2: Emissions Systems Diagnosis
The NOx sensor before an SCR catalyst is intermittently reading zero while the post-SCR sensor reads correctly. Technicians should FIRST check:
48 out of 55
49.
ASE L2: Emissions Systems Diagnosis
After servicing a diesel engine's aftertreatment system, the technician notices excessive soot production during post-service testing. What could be the cause?
49 out of 55
50.
ASE L2: Emissions Systems Diagnosis
When monitoring live data on a diesel engine, a technician observes that the NOx sensor downstream of the SCR system shows a higher reading than the upstream sensor under steady cruising conditions. What does this suggest?
50 out of 55
51.
ASE L2: Emissions Systems Diagnosis
During the forced regeneration of a DPF, the exhaust temperature fails to reach the temperature required to initiate the burn-off. Which of the following could be responsible for this issue?
51 out of 55
52.
ASE L2: Emissions Systems Diagnosis
A technician finds a DPF (Diesel Particulate Filter) pressure differential sensor reading higher than expected on a light load. What is the MOST likely cause of this issue?
52 out of 55
53.
ASE L2: Emissions Systems Diagnosis
An engine's exhaust gas recirculation (EGR) system is suspected of contributing to reduced engine performance. The EGR cooler has passed a pressure test. What is the NEXT best step to diagnose the issue?
53 out of 55
54.
ASE L2: Emissions Systems Diagnosis
A diesel engine vehicle equipped with a DOC (Diesel Oxidation Catalyst) is experiencing higher than normal exhaust temperatures. What is the MOST likely cause?
54 out of 55
55.
ASE L2: Emissions Systems Diagnosis
A diesel engine is found to emit blue smoke at all operating temperatures. Which component should be inspected FIRST for diagnosis?
55 out of 55
