Catalytic Converter Monitor

This monitor applies to DTCs 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. To run monitor, use illustration. See Fig 1. Perform steps as follows:

1. Remove all test equipment from vehicle and install all components and connectors that were removed or disconnected during testing.
2. Start engine.
3. Accelerate to 45 MPH.
4. Travel 5 minutes or more while keeping speed at 45-60 MPH.
5. Decelerate to 35-40 MPH.
6. While keeping accelerator pedal opening degree constant, keep speed at 35-40 MPH for 90 seconds or more.
7. Fully close throttle and decelerate for 10 seconds. Then, quickly accelerate until speed is 35-40 MPH. Then repeat steps  5 and  6 five more times.
8. Return vehicle to shop and turn ignition off.

Fig 1: Running Catalytic Converter Monitor

Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.