ASE Practice Test (L1: Advanced Engine Performance Specialist)

Question 1

A scan tool shows a P0300 random misfire code along with P0301, P0303, P0305 (cylinders 1, 3, 5).
All affected cylinders are on the same bank.
Technician A says a faulty fuel injector on each cylinder is the cause.
Technician B says a restricted fuel injector on that bank or a vacuum leak at the intake manifold gasket is more likely.
Who is correct?

Accepted Answer

Technician B only

Answer

Technician A only

Answer

Both Technician A and Technician B

Answer

Neither Technician A nor Technician B

Question 2

A vehicle has a P0171 (System Lean, Bank 1) code. The long-term fuel trim (LTFT) for Bank 1 is +22%. The MOST likely cause is:

Accepted Answer

A vacuum leak or MAF sensor underreporting air mass on Bank 1

Answer

A rich-biased oxygen sensor on Bank 1

Answer

A faulty fuel pressure regulator causing low fuel pressure system-wide

Answer

Carbon buildup on the Bank 1 oxygen sensor

Question 3

An oscilloscope is connected to the primary circuit of an ignition coil. The waveform shows a ringing pattern with multiple oscillations after the spark line collapses. This indicates:

Accepted Answer

Normal coil operation — oscillations confirm coil energy is dissipating correctly

Answer

The coil primary winding is shorted

Answer

Excessive resistance in the ignition module ground circuit

Answer

A weak spark caused by a fouled spark plug

Question 4

A vehicle with a returnless fuel system has a P0087 (Fuel Rail Pressure Too Low) code. With the engine running, fuel rail pressure is 15 psi below specification. The technician's FIRST test should be:

Accepted Answer

Check for a clogged fuel filter and verify fuel volume delivery at the rail

Answer

Replace the fuel pump — low pressure always indicates a failed pump

Answer

Test the fuel pressure regulator by removing and inspecting the vacuum line

Answer

Perform an injector balance test to check for restricted injectors

Question 5

During an evaporative emission system test, a scan tool shows the EVAP monitor did not complete after two drive cycles. The technician checks and finds the fuel cap passes a pressure test. The NEXT step is:

Accepted Answer

Perform a smoke test on the EVAP system to check for leaks

Answer

Replace the purge solenoid as it is the most common EVAP failure component

Answer

Check the EVAP vent valve for proper operation and sealing

Answer

Clear codes and run a complete OBD-II drive cycle to reset the monitor

Question 6

A vehicle has a complaint of poor fuel economy and sluggish performance. A scan tool shows intake cam timing is retarded 12 degrees from commanded position on Bank 1. The MOST likely cause is:

Accepted Answer

Low oil pressure, a clogged VVT solenoid screen, or a faulty VVT actuator

Answer

A faulty crankshaft position sensor causing timing calculation errors

Answer

Incorrect base ignition timing set by the PCM

Answer

A worn timing chain causing excessive slack and retarded cam timing