Circuit/System Testing

CAUTION: Refer to Heated Oxygen Sensor Resistance Learn Reset Caution .

NOTE: A new converter with less than 161 km (100 mi) on it may set DTC P0420 or P0430 due to out-gassing of the internal matting. Operating the vehicle at highway speeds for approximately 1 h may correct the condition.

Engine idling, observe the DTC information with a scan tool. Verify there are no HO2S or misfire DTCs set.
- If any DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle to diagnosis the applicable DTC before proceeding with this diagnostic procedure.
Verify the following conditions do not exist with the catalytic converter:
- Dents
- A severe discoloration caused by excessive temperatures
- An internal rattle caused by damaged catalyst substrate
- Restrictions-Refer to Restricted Exhaust .
- If a condition is found, replace the catalytic converter.
Verify the following conditions do not exist with the exhaust system:
- Leaks-Refer to Exhaust Leakage .
- Physical damage
- Loose or missing hardware
- Improperly torqued HO2S
- If a condition is found, repair the exhaust system.
Verify the following conditions do not exist with the HO2S 2:
- A grounded wiring harness
- Damage
- If a condition is found, replace the HO2S 2.
If no physical condition is detected and the HO2S 2 is as active as the HO2S 1 after operating the engine at 1,500 RPM for 1 min and then returning to a stabilized idle, then replace the catalytic converter.