ASE4 OBD II and Scan Tool Diagnostics 3

Question 1

What fault condition is indicated by a P0300 diagnostic trouble code?

Accepted Answer

Random or multiple cylinder misfire detected

Answer

Oxygen sensor slow response — Bank 1 Sensor 1

Answer

Knock sensor circuit malfunction — Bank 1

Answer

Crankshaft position sensor signal out of range

Question 2

When Mode $04 is executed from a scan tool, what action does it perform?

Accepted Answer

Clears all stored DTCs, freeze frame data, and resets readiness monitors to incomplete

Answer

Displays all pending DTCs stored in Mode $07 memory

Answer

Retrieves on-board monitoring test results from Mode $06

Answer

Reads the vehicle VIN and ECM calibration identification numbers

Question 3

What data does OBD II Mode $09 contain?

Accepted Answer

Vehicle information including VIN, ECU calibration IDs, and calibration verification numbers

Answer

Oxygen sensor monitoring test results and response times

Answer

All pending and confirmed diagnostic trouble codes

Answer

Evaporative emission system leak test results and purge flow data

Question 4

A P0440 series diagnostic trouble code indicates a fault in which emission control system?

Accepted Answer

Evaporative emission control (EVAP) system

Answer

Exhaust gas recirculation (EGR) system

Answer

Secondary air injection (AIR) system

Answer

Positive crankcase ventilation (PCV) system

Question 5

How does the OBD II catalyst efficiency monitor (P0420) evaluate catalytic converter performance?

Accepted Answer

It compares upstream and downstream O2 sensor switching activity to evaluate oxygen storage capacity

Answer

It measures exhaust backpressure upstream and downstream of the converter

Answer

It requires a wideband UEGO sensor installed downstream of the converter

Answer

It monitors converter temperature rise during a cold start event

Question 6

Which OBD II readiness monitor would most directly be affected by a faulty EVAP purge solenoid valve?

Accepted Answer

Evaporative emission (EVAP) monitor

Answer

Catalyst efficiency monitor

Answer

Upstream oxygen sensor monitor

Answer

Misfire detection monitor

Question 7

When a scan tool shows LTFT of +22% at idle that drops to +3% at 2500 RPM, the most likely diagnosis is:

Accepted Answer

A vacuum leak causing an idle-specific lean condition

Answer

A clogged fuel injector reducing fuel delivery to one cylinder

Answer

A faulty upstream oxygen sensor with a slow response time

Answer

Low fuel pressure due to a failing fuel pump