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

P0300 is the generic OBD II code for a random or multiple cylinder misfire, meaning misfires are not isolated to a single identifiable cylinder.

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

Mode $04 erases all confirmed and pending DTCs, clears associated freeze frame data, and resets all readiness monitors to 'incomplete' status, requiring a new drive cycle to re-complete them.

Question 3

What data does OBD II Mode $09 contain?

Accepted Answer

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

Answer

Mode $09 provides vehicle identification information including the 17-character VIN, ECU calibration identification strings, and CVNs (Calibration Verification Numbers) used to confirm factory programming.

Question 4

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

Accepted Answer

Evaporative emission control (EVAP) system

Answer

P0440 through P0449 codes are assigned to the evaporative emission control system, which captures fuel tank vapors and prevents them from escaping to the atmosphere.

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

The catalyst monitor compares the switching frequency of the upstream (pre-cat) and downstream (post-cat) O2 sensors — a healthy converter stores and releases oxygen, causing the downstream sensor to switch less frequently than the upstream sensor.

ASE4 - ASE Automobile Engine Performance Practice Test

ASE4 - ASE Automobile Engine Performance Practice Test

ASE4 OBD II and Scan Tool Diagnostics 3