ASE4 Computerized Engine Controls 2

Question 1

A P0171 (System Lean Bank 1) and P0174 (System Lean Bank 2) are stored simultaneously. The MOST likely cause is:

Accepted Answer

A large vacuum leak or low fuel pressure affecting both banks

Answer

A leaking injector on one cylinder

Answer

A faulty O2 sensor on Bank 1

Answer

A restricted exhaust on Bank 2

Question 2

A vehicle is in closed-loop with STFT at +22% and LTFT at +20%. The technician should:

Accepted Answer

Investigate the cause of the large positive lean correction

Answer

Accept these values as normal fuel trim variation

Answer

Clear the adaptations and retest

Answer

Replace the downstream O2 sensor

Question 3

What does a P0300 code (Random/Multiple Cylinder Misfire) indicate?

Accepted Answer

Misfires are detected across multiple cylinders or cannot be isolated to one

Answer

Only cylinder #1 is misfiring

Answer

The ignition system has failed completely

Answer

The fuel injectors are all misfiring in sequence

Question 4

A scan tool shows the ECT (engine coolant temperature) PID reads 195°F with the engine warm. The cooling fan is cycling normally. This reading indicates:

Accepted Answer

Normal operating temperature

Answer

The thermostat is stuck open

Answer

Overheating and the thermostat is stuck closed

Answer

The ECT sensor is faulty

Question 5

A technician notices LTFT is -15% on both banks. This indicates the ECM is removing fuel because the engine is:

Accepted Answer

Running rich and subtracting fuel to maintain stoichiometry

Answer

Running lean and compensating by adding fuel

Answer

Operating normally with slight enrichment for performance

Answer

Experiencing a vacuum leak

Question 6

Which condition will cause the ECM to enter open-loop mode even with a warm engine?

Accepted Answer

Hard acceleration (WOT enrichment)

Answer

High fuel trim values

Answer

EGR system activation

Answer

Idle fuel control