ASE Practice Test #1 2

Question 1

A vehicle has a misfire on cylinder 3 only. The spark plug, ignition coil, and injector have been swapped with cylinder 4 and the misfire stayed on cylinder 3. What does this indicate?

Accepted Answer

The problem is mechanical in nature — likely low compression, a burned valve, or a leak — specific to cylinder 3, since the components tested good in another cylinder

Answer

The ignition coil is faulty

Answer

The engine control module needs replacement

Answer

The fuel injector for cylinder 3 is still faulty

Question 2

What does a negative fuel trim (negative short-term fuel trim, STFT) reading indicate?

Accepted Answer

The ECM is reducing fuel delivery because the oxygen sensor is indicating a rich condition — more oxygen is being burned than expected

Answer

The engine is running lean and needs more fuel

Answer

The fuel pressure is too low

Answer

The MAF sensor is reading too low

Question 3

An ABS warning light is on and a scan tool shows a left front wheel speed sensor DTC. Which test most efficiently verifies sensor operation?

Accepted Answer

Use the scan tool to view live wheel speed data while spinning the wheel by hand — a functioning sensor should produce a changing speed reading; no change indicates a failed sensor or gap/tone ring issue

Answer

Replace the wheel speed sensor immediately

Answer

Measure battery voltage at the sensor connector

Answer

Perform a road test at 50 MPH and recheck the code

Question 4

When performing a battery drain (parasitic draw) test, what is the maximum acceptable draw on a modern vehicle with keyless entry and a body control module in sleep mode?

Accepted Answer

50 milliamps (50mA) or less, depending on manufacturer specification

Answer

500 milliamps (0.5A)

Answer

200 milliamps (0.2A)

Answer

1 amp (1000mA)

Question 5

What is the purpose of a variable valve timing (VVT) system in a gasoline engine?

Accepted Answer

To optimize valve timing for different engine operating conditions, improving power at high RPM, torque at low RPM, and fuel efficiency throughout the RPM range

Answer

To eliminate the need for an ignition system

Answer

To vary the compression ratio of the engine

Answer

To control spark advance only

Question 6

A vehicle has a check engine light and a DTC P0420 (Catalyst System Efficiency Below Threshold). Which test should be performed FIRST before replacing the catalytic converter?

Accepted Answer

Check for engine misfires, oil burning, coolant leaks, exhaust leaks before the upstream O2 sensor, and verify upstream/downstream O2 sensor operation — any of these can cause P0420 without a failed converter

Answer

Replace the catalytic converter immediately as P0420 always means the converter is bad

Answer

Replace both oxygen sensors first

Answer

Check the fuel cap for tightness