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The ASE L2 exam has 55 questions and runs 2 hours.
These 10 free ASE L2 questions are organized by exam domain, so you can see how each part of the ASE Electronic Diesel Engine Diagnosis Specialist (L2) blueprint is tested. Reveal the answer and explanation under each question.
A medium-duty truck develops dense white exhaust only after warm-up. The exhaust has a sweet odor, coolant level falls, cylinder cutout changes engine speed normally on all six cylinders, and fuel rail pressure tracks desired. The EGR cooler outlet is wet when the cooling system is pressure-tested. The most likely fault is:
Correct answer: C - An internally leaking EGR cooler
On the Type 4 composite vehicle, coolant temperature is steady at 237°F during a controlled loaded test. The sensor agrees with an infrared check, the fan is on, and no shutdown-level oil or coolant-level condition is present. Type 4 coolant protection specifies 20% derate at 225°F, 40% at 230°F, 60% at 235°F, and shutdown at 240°F. The ECM should now command:
Correct answer: A - A 60% engine derate without a coolant-temperature shutdown
After key-off, a technician waits more than 120 seconds for the Type 4 J1939 network to sleep, disconnects power as required, and measures 120 Ω across CAN_H and CAN_L. The network uses two 120 Ω terminating resistors. This 120 Ω reading indicates:
Correct answer: D - One terminating resistor or its branch is open
An EGR actuator operates slowly only when commanded against spring load. With the circuit de-energized, the harness shows 0.3 Ω end-to-end. With the actuator operating, the connector accounts for 1.8 V of the circuit's total drop and becomes warm. These test results identify:
Correct answer: B - The connector has excessive resistance under load
On the Type 4 accelerator pedal, APP 1 must remain 1.00 V higher than APP 2 throughout travel; a correlation failure places the engine at idle only. At 50% pedal, APP 1 is 3.00 V and APP 2 is 2.70 V, and both signals rise smoothly when the pedal is moved. The appropriate ECM response is to:
Correct answer: B - Set a correlation fault and limit the engine to idle
Four unrelated pressure and position sensors set voltage-low DTCs at the same instant after the harness rubs through near a bracket. All four sensors share one 5 V reference, while their individual signal wires are on separate branches. Diagnosis should begin by:
Correct answer: D - Test the shared 5 V reference for a short to ground
A commanded VGT sweep shows normal actuator supply voltage and current. The ECM command moves from 15% to 85%, but position feedback and the observed external lever both stay near 18%. The active DTC carries FMI 7, defined as mechanical system not responding or out of adjustment. The next test should focus on:
Correct answer: A - Inspect the VGT mechanism for binding and verify actuator calibration
After an overnight cold soak at 70°F, the coolant-temperature PID reads −40°F and the signal measures 4.5 V. The Type 4 NTC table maps 4.5 V to −40°F; colder temperature corresponds to higher resistance and higher signal voltage. The 5 V reference and low-reference circuits test good, and an approved jumper from signal to low reference drives the PID to the hot limit. The signal behavior is most consistent with:
Correct answer: C - An open NTC sensor element or poor terminal contact
During a slick-road event, engine torque drops for three seconds. Fuel supply and rail pressure remain on target, no engine DTC sets, and the ECM records an active torque-reduction request from the stability/traction controller for exactly the same interval. The data show that:
Correct answer: A - The stability controller intentionally requested the torque reduction
After ECM replacement, the truck reaches its programmed road-speed limit much earlier than before, but engine power, raw vehicle-speed sensor frequency, and transmission operation are normal. The replacement ECM contains an axle ratio and tire-revolutions-per-mile value from a different vehicle. Before installing more hardware, correct:
Correct answer: D - The ECM's programmable vehicle configuration
The ASE L2 exam also covers these domains. Drill them in the full free practice test:
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