Circuit/System Testing

Inspect the catalytic converter for the following conditions:
- Physical damage
- A severe discoloration caused by excessive temperatures
- An internal rattle caused by damaged catalyst substrate
- Restrictions
  - If a condition is found, replace the catalytic converter.
Inspect the exhaust system for the following conditions:
- Leaks before the converter
- Physical damage
  - If a condition is found, replace the exhaust system, or components as necessary.
Inspect the HO2S 2 sensor and circuits for the following conditions:
- A grounded or chafing wiring harness
- Physical damage
  - If a condition is found, replace the HO2S 2 sensor.
Inspect the HO2S 2 sensor for proper torque.
- If the HO2S 2 sensor has improper torque, correctly torque the sensor.
If no physical condition is detected perform the following:
- Clear all of the DTCs.
- Operate the vehicle under the conditions for running the DTC.
- If DTC P0420 runs, fails and illuminates the MIL, replace the catalytic converter.