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The ASE A9 exam has 60 questions and runs 1 hour 15 minutes.
These 10 free ASE A9 questions are organized by exam domain, so you can see how each part of the ASE A9 Light Vehicle Diesel Engines blueprint is tested. Reveal the answer and explanation under each question.
A diesel intermittently loses power only during a sustained highway climb. A stored boost-control DTC has freeze-frame data at 2,300 rpm, 78% load, and normal coolant temperature. A chafed actuator wire is repaired. After the original data are recorded and the DTC is cleared, the best verification step is to:
Correct answer: A - Repeat the highway-load condition and compare commanded with actual data
A fully warmed diesel produces persistent sweet-smelling white vapor, and the coolant level is falling. After the engine cools, a pressure transducer on the cooling system shows pulses synchronized with cranking while injection is disabled. Taken together, these findings most strongly indicate:
Correct answer: C - A cylinder-to-coolant leak through the head gasket or a cracked casting
Service information requires at least 220 rpm cranking speed. A no-start cranks at 182 rpm; battery voltage falls to 8.9 V, CKP/CMP synchronization changes between YES and NO, and desired rail pressure is much higher than actual. The technician should first:
Correct answer: B - Restore specified cranking speed, then reevaluate synchronization and rail pressure
On an engine with one rocker operating two exhaust valves through an adjustable bridge, lash was set before the bridge was equalized. One valve now has less lift and heavier tip contact than the other. What should be done before final lash is set again?
Correct answer: D - Equalize the bridge on both valve stems, then reset lash
During cylinder-head installation, one bolt reaches the initial torque before its head seats. The bolt is removed and coolant is found in the bottom of the blind hole. The correct response is to:
Correct answer: B - Clean and dry the hole, inspect bolt and threads, then follow service information
A cylinder is measured in the thrust axis at the same temperature: 4.0040 in near the top and 4.0005 in near the bottom. The service limit for taper is 0.0020 in. What are the taper and service conclusion?
Correct answer: C - 0.0035 in; the bore exceeds the limit
A newly installed connecting-rod bearing develops bright polished wear only along one edge. The crankpin diameter, taper, and out-of-round are within specification, oil supply is verified, and debris is absent. Which follow-up check best addresses the wear pattern?
Correct answer: A - Measure rod bend, twist, and big-end bore alignment
At hot idle, the dash oil-pressure warning is on and scan data shows 4 psi. A calibrated mechanical gauge reads 22 psi; the service minimum is 15 psi. Technician A says actual base-engine oil pressure is acceptable. Technician B says the pressure-sensor, wiring, or display path should be diagnosed. Who is correct?
Correct answer: C - Both technicians are correct
A diesel maintains normal coolant temperature at highway speed but overheats during extended idle. The radiator core is unobstructed, coolant level is correct, fan command is 96%, and actual fan speed remains zero. What fault is most consistent with this operating pattern?
Correct answer: D - A fan drive, power-supply, or control failure
During a loaded road test, desired and actual VGT position agree. Desired boost is 22 psi, actual boost is 9 psi, black smoke is present, and a regulated charge-air test reveals a large leak at the cooler end tank. Which diagnosis is best supported?
Correct answer: B - A charge-air cooler leak reducing delivered air mass
The ASE A9 exam also covers these domains. Drill them in the full free practice test:
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