SCT OBD Systems & Diagnostics 3

Question 1

What is 'freeze frame' data captured and stored by an OBD II system?

Accepted Answer

A snapshot of engine operating conditions recorded at the moment a DTC was set

Answer

Data showing only the vehicle speed when the MIL first illuminated

Answer

A recording of engine sensor data across the last five complete drive cycles

Answer

Real-time sensor data accessible only through a factory-level scan tool

Question 2

Which of the following OBD II monitors is classified as a 'continuous' monitor that runs at all times while the engine is operating?

Accepted Answer

Misfire monitor

Answer

Catalyst monitor

Answer

EVAP monitor

Answer

Oxygen sensor monitor

Question 3

For California smog inspections of 2001 and newer OBD II vehicles, what is the maximum number of readiness monitors allowed to show 'not ready' while still permitting the vehicle to pass?

Accepted Answer

One monitor may be incomplete

Answer

Zero — all monitors must be complete

Answer

Two monitors may be incomplete

Answer

No limit, provided no DTCs are stored and MIL is off

Question 4

What does long-term fuel trim (LTFT) data of consistently +20% or higher indicate about engine operation?

Accepted Answer

The engine has been running lean and the ECM is adding extra fuel to compensate

Answer

The engine is running normally with an intentionally rich fuel mixture

Answer

The catalytic converter has reached the end of its useful service life

Answer

The upstream oxygen sensors are reading abnormally high voltage

Question 5

Which OBD II service mode (Mode) is used to request current powertrain diagnostic data and view live sensor readings?

Accepted Answer

Mode $01

Answer

Mode $02

Answer

Mode $03

Answer

Mode $04

Question 6

What does diagnostic trouble code P0420 indicate in an OBD II system?

Accepted Answer

Catalytic converter efficiency below threshold — Bank 1

Answer

Oxygen sensor circuit malfunction — Bank 1 Sensor 1

Answer

EVAP system large leak detected

Answer

Mass airflow sensor circuit range/performance malfunction

Question 7

What is the primary purpose of checking OBD II I/M readiness status during a California smog inspection?

Accepted Answer

To confirm the vehicle's emission control self-tests are complete and no faults have been detected

Answer

To verify the vehicle's VIN matches the registration documentation

Answer

To directly measure tailpipe hydrocarbon and CO concentrations in real time

Answer

To verify the accuracy of the vehicle's odometer reading