ASE4 Emission Control Systems 3

Question 1

A knock sensor detects detonation. What does the ECM do in response?

Accepted Answer

Retards ignition timing to eliminate detonation

Answer

Advances ignition timing to clear the knock

Answer

Enriches the fuel mixture to reduce knock

Answer

Increases EGR flow to cool combustion

Question 2

The EVAP large leak code P0455 is set. A smoke test finds smoke exiting from around the fuel cap. The correct repair is to:

Accepted Answer

Replace the fuel cap and retest

Answer

Replace the entire EVAP canister assembly

Answer

Replace the purge solenoid

Answer

Replace the vent solenoid

Question 3

Which scan tool parameter BEST indicates whether the catalytic converter is working efficiently?

Accepted Answer

Comparison of upstream and downstream O2 sensor activity

Answer

Upstream O2 sensor switching frequency

Answer

EGR flow percentage

Answer

Fuel trim values on both banks

Question 4

A vehicle has high NOx readings on an emissions test but passes HC and CO. The MOST likely cause is:

Accepted Answer

A faulty or clogged EGR system

Answer

A rich fuel mixture

Answer

A leaking fuel injector

Answer

A failed oxygen sensor

Question 5

A continuous EVAP monitor detects a large leak during normal driving. The vent solenoid is commanded closed and the purge solenoid is commanded open. The system then monitors:

Accepted Answer

Vacuum decay in the EVAP system

Answer

Fuel pressure changes

Answer

Oxygen sensor voltage

Answer

MAP sensor pressure

Question 6

Carbon monoxide (CO) is primarily produced when:

Accepted Answer

The engine runs rich, leaving insufficient oxygen to complete combustion

Answer

Combustion temperatures are too high

Answer

Combustion temperatures are too low for HC oxidation

Answer

The EGR valve is stuck open