ASE Advanced Engine Performance Specialist 2

Question 1

A wide-band (air/fuel ratio) oxygen sensor differs from a conventional narrow-band sensor primarily because it can:

Accepted Answer

Measure the exact air/fuel ratio across a wide range

Answer

Wide-band sensors use a pump cell to report the precise AFR across a broad range rather than just switching at stoichiometry.

Question 2

A vehicle shows high long-term fuel trim (e.g., +25%) at idle but normal trim at cruise. The MOST likely cause is:

Accepted Answer

A vacuum leak

Answer

A vacuum leak has the greatest proportional effect at idle when airflow is low, driving fuel trims positive.

Question 3

When diagnosing a P0301 (cylinder 1 misfire), the technician should FIRST:

Accepted Answer

Verify the misfire follows the cylinder by swapping coil/injector

Answer

Swapping components to a different cylinder shows whether the fault moves, isolating coil/injector versus a mechanical issue.

Question 4

A relative compression test using a current clamp on the starter is useful because it:

Accepted Answer

Identifies a weak cylinder without removing spark plugs

Answer

Cranking current variation reveals a low-compression cylinder quickly without disassembly.

Question 5

A MAF sensor reading lower than expected grams-per-second at wide-open throttle will typically cause:

Accepted Answer

A lean condition and possible hesitation

Answer

An underreporting MAF tells the ECM less air is entering, so it commands less fuel, creating a lean condition.

ASE Practice Test