Catalytic Converter Monitor
PCM monitors the deterioration of catalyst by the output frequency ratio between heated oxygen sensor (front) and heated oxygen sensor (rear).
This monitor applies to DTC P0421 and P0431. Following conditions must be met during the test:
- Atmospheric temperature is 14°F (-10°C) or more.
- A/C switch is in OFF position.
- Selector lever is in "D" range.
Monitor takes about 20 minutes to complete. This cycle must be completed 2 times. Run monitor as shown. See Fig 1 . Remove all test equipment from vehicle and install all components and connectors that were removed or disconnected during testing. Perform steps as follows:
- Start engine and accelerate to 45 MPH.
- Travel 300 seconds or greater while keeping speed at 45-60 MPH.
- Fully close throttle and decelerate to 35-40 MPH.
- While keeping accelerator pedal opening degree constant, keep speed at 35-40 MPH for 90 seconds or more (this is when monitor runs).
- Fully close throttle and decelerate for 10 seconds. Then, quickly accelerate until speed is 35-40 MPH. Then repeat steps 3 and 4 five more times.
- Return vehicle to shop and Turn the ignition switch to LOCK position. Recheck for DTCs. If DTC P0421 or P0431 resets, return to appropriate repair procedure under DIAGNOSTIC TESTS