ASE4 Engine Electrical Systems 3

Question 1

A vehicle with a smart charging system shows 12.6V on the scan tool but 14.4V on a voltmeter at the battery. The discrepancy is because:

Accepted Answer

The BCM is reporting battery voltage, not alternator output voltage

Answer

The scan tool reads the BCM's internal battery voltage sense circuit, while the voltmeter reads actual terminal voltage — these can differ due to sensor location or calibration.

Question 2

A no-start complaint: the engine cranks normally but will not start. Battery and charging tests are normal. The technician should next check:

Accepted Answer

Spark, fuel pressure, and injector pulse with a noid light

Answer

Normal crank speed with a no-start condition means the electrical starting circuit is good; the next step is to verify the three elements of combustion: spark, fuel, and injector control.

Question 3

Excessive AC ripple on the charging circuit (above 0.5 volts AC) can cause:

Accepted Answer

ECM and module faults, erratic sensor readings, and communication errors

Answer

AC ripple from a failing alternator diode introduces electrical noise that can disrupt ECM operation and cause numerous unrelated electronic faults.

Question 4

The purpose of the battery's CCA (Cold Cranking Amps) rating is to indicate:

Accepted Answer

The current a battery can deliver at 0°F for 30 seconds while maintaining 7.2 volts

Answer

CCA specifies the battery's ability to deliver high current at cold temperatures, directly reflecting its starting capability in winter conditions.

Question 5

A voltage drop test on the ground side of the starting circuit shows 0.6 volts. This indicates:

Accepted Answer

Excessive resistance in the ground circuit reducing starter power

Answer

Ground-side voltage drops above 0.1–0.2 volts indicate resistance that robs the starter of available voltage, causing slow or difficult cranking.

ASE4 - ASE Automobile Engine Performance Practice Test

ASE4 - ASE Automobile Engine Performance Practice Test

ASE4 Engine Electrical Systems 3