Before a road test to reproduce an intermittent misfire DTC, the technician wants the engine speed, load and temperature ranges within which the PCM runs its misfire diagnostic. Where is this found?

In the DTC's enabling conditions in service information

In the freeze frame data stored with the DTC

In the misfire monitor's readiness status on the scan tool

In the on-board test results (Mode $06) for misfire

An ignition coil passes the manufacturer's primary and secondary resistance checks, yet the misfire it causes appears only under heavy load and moves with the coil when coils are swapped. Why can the resistance test miss this fault?

Its few volts cannot stress insulation that fails at firing voltage

Coil resistance drops as the coil warms, hiding the fault when hot

The PCM shortens coil on-time under load, which an ohmmeter can't show

Firing voltage falls under load, so a weak coil fails only then

A four-wheel-drive pickup stores P0300 “Random/Multiple Cylinder Misfire Detected” only after trips on washboard gravel roads. The driver feels no misfire, and on pavement, hard pulls included, the misfire counters stay at 0. The service information says the PCM uses ABS wheel-speed data, sent over the network, to recognize rough roads and suspend misfire detection. The ABS warning lamp is on with a wheel speed sensor DTC stored. Which of these could be the cause?

The PCM is not receiving rough-road data from the ABS module

Ignition coils that break down when the engine is under load

A crankshaft position sensor air gap that is too wide

Water in the fuel causing intermittent lean misfires

After a crankshaft front seal and damper replacement, an engine lacks power and sets a camshaft/crankshaft position correlation DTC. Its CKP sensor reads a reluctor ring pressed onto the crankshaft behind the damper. With the damper's mark confirmed at top dead center using a piston stop, a timing light shows 8° BTDC at 2,000 rpm while the timing advance PID reads 23° BTDC and the knock retard PID reads 0°. Which of these could be the cause?

The reluctor ring has turned on the crankshaft

The timing chain has jumped a tooth at the crankshaft

The new damper's outer ring has slipped on its hub

The PCM is retarding the spark for detected knock

ASE L1 Ignition Diagnosis Practice Questions

Five free practice questions on ignition system diagnosis: content area C of the ASE L1 Advanced Engine Performance Specialist test, 6 of its 50 scored questions (12%). They are in the ASE format: four options, one best answer. Answer each one before opening the explanation. No account, no email.

01The questions

Recall · Ignition System Diagnosis

Before a road test to reproduce an intermittent misfire DTC, the technician wants the engine speed, load and temperature ranges within which the PCM runs its misfire diagnostic. Where is this found?
1. In the DTC's enabling conditions in service information
2. In the freeze frame data stored with the DTC
3. In the misfire monitor's readiness status on the scan tool
4. In the on-board test results (Mode $06) for misfire
Show the answer

A. Correct. The service information's description of each DTC lists the conditions for running the diagnostic (its enable criteria) and for setting the code. Knowing those ranges lets the road test put the engine where the PCM actually checks for the fault.

Why not the others

B. Freeze frame is one snapshot of the conditions when the fault was first detected, not the ranges in which the diagnostic runs; it helps choose where to start, while the enable criteria come from the DTC description.

C. A readiness status only says whether a monitor has finished, and misfire monitoring runs continuously; it lists no speed, load or temperature ranges, which are in the DTC's enabling conditions.

D. On-board test results show measured values and limits from tests already run, not the conditions under which the diagnostic is allowed to run; those enable criteria are in the DTC description.
Recall · Ignition System Diagnosis

An ignition coil passes the manufacturer's primary and secondary resistance checks, yet the misfire it causes appears only under heavy load and moves with the coil when coils are swapped. Why can the resistance test miss this fault?
1. Coil resistance drops as the coil warms, hiding the fault when hot
2. Its few volts cannot stress insulation that fails at firing voltage
3. The PCM shortens coil on-time under load, which an ohmmeter can't show
4. Firing voltage falls under load, so a weak coil fails only then
Show the answer

B. Correct. An ohmmeter pushes a tiny current at a few volts, while under load the coil must make far higher secondary voltage; cracked or weakened insulation can hold at low voltage and arc through at high voltage. A scope on the secondary under load, or a known-good coil, finds this fault.

Why not the others

A. Copper winding resistance rises, not falls, as a coil warms, and a resistance shift would not explain an insulation failure; the ohmmeter misses the fault because its low voltage never stresses the insulation.

C. Coil on-time is set mainly by system voltage and engine speed, not cut back by load; the real reason is that the ohmmeter's low voltage cannot reveal insulation that breaks down at high voltage.

D. Required firing voltage rises under load as cylinder pressure rises; that higher voltage is what breaks through weak insulation, which a low-voltage ohmmeter cannot do.
Diagnosis · Ignition System Diagnosis

A four-wheel-drive pickup stores P0300 “Random/Multiple Cylinder Misfire Detected” only after trips on washboard gravel roads. The driver feels no misfire, and on pavement, hard pulls included, the misfire counters stay at 0. The service information says the PCM uses ABS wheel-speed data, sent over the network, to recognize rough roads and suspend misfire detection. The ABS warning lamp is on with a wheel speed sensor DTC stored. Which of these could be the cause?
1. The PCM is not receiving rough-road data from the ABS module
2. Ignition coils that break down when the engine is under load
3. A crankshaft position sensor air gap that is too wide
4. Water in the fuel causing intermittent lean misfires
Show the answer

A. Correct. The PCM finds misfires as brief changes in crankshaft speed, and washboard jolts through the driveline look the same. With the ABS fault, the PCM loses the wheel-speed data it uses to spot rough roads, so it counts those jolts as misfires; repair the wheel speed sensor fault, then recheck on the same road.

Why not the others

B. Coils that break down under load would also misfire during hard pulls on pavement, and the driver would feel it; here the counters stay at 0 on pavement and the counts appear only on rough roads while rough-road data is lost.

C. A wide CKP air gap weakens the signal on every road surface, so it would not confine the counts to gravel; the link to rough roads and the stored ABS fault point to the missing rough-road data.

D. Water in the fuel would cause misfires the driver could feel on any road, pavement included; these counts appear only on rough roads with the ABS fault present, which points to the lost rough-road data.
Tech ab · Ignition System Diagnosis

A pickup misfires only when pulling a heavy trailer up long grades, and the misfire never appears in the shop. Technician A says raising engine speed to 2,500 rpm in Park with no load will raise cylinder pressure enough to reproduce it. Technician B says watching the secondary ignition pattern during a loaded road test or on a chassis dynamometer can reproduce it. Who is right?
1. A only
2. B only
3. Both A and B
4. Neither A nor B
Show the answer

B. Correct. Technician B is right: the voltage needed to fire a plug rises with cylinder pressure, which is highest at large throttle openings under load, so a loaded road test or a dynamometer recreates the stress that exposes the weak part. Technician A is wrong, because a no-load rev in Park leaves the cylinders lightly filled.

Why not the others

A. Technician A is wrong: with no load the throttle opens only a little, so cylinder filling, and with it the voltage needed to fire the plugs, stays low. Technician B is right: loading the engine raises cylinder pressure and firing voltage the way the trailer does.

C. Only Technician B is right. Technician A's no-load rev in Park keeps manifold vacuum high and cylinder pressure low, so it does not stress the ignition the way pulling a trailer up a grade does.

D. Technician B is right: a loaded road test or a dynamometer raises cylinder pressure and firing voltage as the trailer does. Technician A is wrong, because a no-load rev in Park leaves cylinder pressure low.
Diagnosis · Ignition System Diagnosis

After a crankshaft front seal and damper replacement, an engine lacks power and sets a camshaft/crankshaft position correlation DTC. Its CKP sensor reads a reluctor ring pressed onto the crankshaft behind the damper. With the damper's mark confirmed at top dead center using a piston stop, a timing light shows 8° BTDC at 2,000 rpm while the timing advance PID reads 23° BTDC and the knock retard PID reads 0°. Which of these could be the cause?
1. The reluctor ring has turned on the crankshaft
2. The timing chain has jumped a tooth at the crankshaft
3. The new damper's outer ring has slipped on its hub
4. The PCM is retarding the spark for detected knock
Show the answer

A. Correct. The PCM times each spark from the reluctor teeth, so a ring turned on the crankshaft moves every spark by the same angle while the PCM believes its command is met; the 23 - 8 = 15° gap between PID and light shows it. The shifted ring also moves the CKP signal against the camshaft signals, which sets the correlation DTC.

Why not the others

B. A jumped chain moves the camshafts and can set a correlation DTC, but the spark is still timed from the crankshaft reluctor, so the timing light would agree with the PID; it cannot make a 15° difference.

C. The piston stop confirmed the damper mark at true top dead center, so the mark is accurate; the light is reading the real spark timing, which is 15° behind the command.

D. The knock retard PID reads 0°, so the PCM is not taking timing out for knock, and knock retard would not set a camshaft/crankshaft correlation DTC either; the 15° gap comes from where the spark is referenced.

02Answer key

Question	Answer
Q1	A
Q2	B
Q3	A
Q4	B
Q5	A

03What area C covers

This content area covers electronic ignition systems, meaning distributorless, coil-on-plug and coil-near-plug designs: separating ignition electrical faults from mechanical ones, diagnosing the no-start, misfire, knock, power loss and emission problems the ignition causes, testing the system under different engine loads, reading ignition waveforms, confirming spark timing and its control, and tracing single, multiple and repeated failures to a root cause.

The ASE test specification calls this content area “Ignition System Diagnosis”. It carries 6 of the 50 scored questions, 12% of the test.

Confirm the concern and check for tampered parts
Separate ignition electrical faults from mechanical ones
Diagnose misfire, no-start, knock and power loss from ignition faults
Test the ignition system under different engine loads
Read ignition waveforms on a scope
Confirm spark timing and how it is controlled
Find root causes, including repeat failures
Verify the repair

04What the questions turn on

Recreate the load

The voltage needed to fire a plug rises with cylinder pressure, which is highest under load. A no-load rev in Park does not stress the ignition that way, and an ohmmeter's few volts cannot find insulation that breaks down at firing voltage.

The timing PID is calculated

The timing advance PID is the advance the PCM has calculated, not a measurement. Actual timing is checked against crankshaft position with a timing light on a verified mark or a scope. A reluctor ring turned on the crankshaft shifts every spark.

Low firing line, low compression

The voltage needed to jump a plug gap falls with cylinder pressure. One cylinder with a low firing line while its coil current ramp matches the others can point to low compression, a mechanical fault, rather than an ignition fault.

Composite vehicle strategies

In the composite vehicle questions, the answer can come from the reference booklet's strategy. Losing one CMP signal sets a DTC and parks valve timing fully retarded, but the engine still runs. The coil drivers are inside the ECM, with no separate ignition module.

05The other content areas

The L1 test has six content areas. Each has its own page of free questions:

The ASE L1 Advanced Engine Performance Specialist practice test page describes the full question bank. How these questions are written and checked: how our questions are made. Found a mistake? Tell us and we will fix it.

ToolboxPrep is an independent study site. It is not affiliated with or endorsed by ASE (the National Institute for Automotive Service Excellence). Our questions are original practice questions written to the published ASE test specifications; they are not actual test questions.