Circuit/System Testing
CAUTION:
Refer to Three-Way Catalytic Converter Damage Caution
.
CAUTION:
Refer to Heated Oxygen Sensor Resistance Learn Reset Caution
.
NOTE:
A new converter with less than 100 miles on it may set DTC P0420 due to out-gassing of the internal matting. Operating the vehicle at highway speeds for approximately 1 hour may correct the condition.
- If any other DTCs are set perform those diagnostics first.
- Inspect for the following conditions which may cause a catalytic converter to degrade:
- An engine misfire
- High engine oil or high coolant consumption
- Retarded spark timing
- A weak or poor spark
- A lean fuel mixture
- A rich fuel mixture
- A damaged oxygen sensor or wiring harness
- The catalyst test may abort if the vehicle falls outside the conditions for running the DTC.
- A catalyst may be temporarily degraded if a fuel with high sulfur content has been used. Drive the vehicle at highway speeds for 10 minutes and retest the converter.
- Operate the vehicle within the Conditions for Running the DTC.
- If the DTC fails this key cycle, continue with this procedure.
- Inspect the catalytic converter for the following conditions:
- Dents
- A severe discoloration caused by excessive temperatures
- Road damage
- 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
- Physical damage
- Loose or missing hardware
- Properly torqued heated oxygen sensor (HO2S)
- Restrictions
- If a condition is found, repair the exhaust system.
- Inspect the post catalyst HO2S for the following conditions:
- A grounded wiring harness
- Damage
- If a condition is found, replace the post catalyst HO2S.
- If no physical condition is detected, replace the catalytic converter.
- Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.