SCT OBD Systems & Diagnostics 2

Question 1

What DTC prefix indicates a generic (SAE-standardized) emissions-related powertrain fault in the OBD II system?

Accepted Answer

P0 (Generic Powertrain)

Answer

P0 codes are generic SAE-standardized powertrain diagnostic trouble codes, and most emissions-related faults are classified under this category.

Question 2

What does a 'pending' DTC in an OBD II system indicate?

Accepted Answer

A fault detected once but not yet confirmed through a second drive cycle

Answer

A pending DTC means the OBD II system detected a potential fault during one drive cycle but requires confirmation in a second drive cycle before setting a confirmed code and illuminating the MIL.

Question 3

What engine parameter does OBD II standard PID $05 (Mode 01, PID 05) report?

Accepted Answer

Engine coolant temperature

Answer

OBD II PID $05 reports engine coolant temperature, which is critical for verifying the engine has reached normal operating temperature before accurate emission tests can be performed.

Question 4

How many consecutive confirmed detections (drive cycles) does an OBD II system typically require before setting a confirmed DTC and illuminating the MIL?

Accepted Answer

Two consecutive drive cycles

Answer

Most OBD II monitors require a fault to be detected in two consecutive drive cycles before setting a confirmed DTC and illuminating the MIL, helping prevent false positives from transient conditions.

Question 5

What does the OBD II oxygen sensor monitor evaluate during its self-test?

Accepted Answer

The response time and output voltage range of upstream and downstream O2 sensors

Answer

The oxygen sensor monitor evaluates the switching frequency, response time, and voltage output of both upstream (pre-cat) and downstream (post-cat) O2 sensors to verify proper fuel control feedback.

SCT - Smog Check Technician Certification Practice Test

SCT - Smog Check Technician Certification Practice Test

SCT OBD Systems & Diagnostics 2