ASE Practice Test #5 2

Question 1

A technician performs a relative cylinder compression test (cylinder contribution test) and finds cylinder 4 has the lowest contribution. What is the NEXT step to determine the root cause?

Accepted Answer

Perform a conventional compression test followed by a cylinder leakdown test on cylinder 4 to differentiate between compression loss (rings, valves) and ignition/fuel issues

Answer

Replace the spark plug and ignition coil on cylinder 4 immediately

Answer

Replace the head gasket on cylinder 4 bank

Answer

Check the fuel injector balance rate on cylinder 4 only

Question 2

What does a KOEO (Key On Engine Off) test reveal that a KOER (Key On Engine Running) test does not?

Accepted Answer

KOEO tests check electrical circuit integrity and hard faults stored in memory without the influence of running engine conditions; KOER tests additional sensor and actuator performance under operating conditions

Answer

KOEO tests show only running faults; KOER shows stored faults

Answer

There is no difference between KOEO and KOER tests

Answer

KOEO tests require a dynamometer; KOER tests do not

Question 3

A technician measures a thermistor (NTC type) sensor resistance. As the temperature increases, what happens to the resistance reading?

Accepted Answer

Resistance decreases as temperature increases — NTC stands for Negative Temperature Coefficient

Answer

Resistance increases as temperature increases

Answer

Resistance stays constant regardless of temperature

Answer

Resistance alternates between high and low as temperature rises

Question 4

What is the function of variable displacement (cylinder deactivation) technology in a V6 or V8 engine?

Accepted Answer

To deactivate specific cylinders (closing their valves and stopping fuel injection) during light load conditions, reducing the effective engine displacement and significantly improving fuel economy

Answer

To automatically switch from gasoline to diesel fuel during highway driving

Answer

To increase displacement during heavy acceleration by adding additional displacement through variable compression pistons

Answer

To rotate which cylinders fire each revolution for even wear

Question 5

A technician uses a scan tool and finds the O2 sensor upstream (pre-catalyst) is switching normally, but the downstream O2 sensor reads a steady 0.1V. What does a steady low voltage downstream O2 sensor indicate?

Accepted Answer

Permanently lean downstream exhaust — possible causes include an exhaust leak between the upstream sensor and converter, or a failed catalyst that is not processing the exhaust gases at all (letting lean exhaust pass through)

Answer

The catalyst is functioning correctly

Answer

The downstream O2 sensor is shorted to ground

Answer

The ECM is commanding open-loop operation

Question 6

A vehicle's traction control system activates unexpectedly on dry pavement with no wheel slip occurring. Which component failure is MOST likely causing false traction control activation?

Accepted Answer

A wheel speed sensor producing an erratic or intermittent signal — the ABS/traction control module interprets the false speed reading as wheel slip and activates traction control unnecessarily

Answer

Failing brake master cylinder

Answer

Low engine oil level

Answer

Faulty throttle position sensor

A technician performs a relative cylinder compression test (cylinder contribution test) and finds cylinder 4 has the lowest contribution.What is the NEXT step to determine the root cause?

A technician performs a relative cylinder compression test (cylinder contribution test) and finds cylinder 4 has the lowest contribution.
What is the NEXT step to determine the root cause?