Circuit/System Testing

WARNING: This page is about a different car, the 2010 GMC Sierra and 2010 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.

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 or P0430 due to out-gassing of the internal matting. Operating the vehicle at highway speeds for approximately 1 hour may correct the condition.

Ignition ON, observe the DTC information with a scan tool. Verify that no HO2S or misfire DTCs are set.
- If a DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle for further diagnosis before proceeding with this diagnostic procedure.
Inspect the catalytic converter for the following conditions:
- Dents
- 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-Refer to Exhaust Leakage .
- Physical damage
- Loose or missing hardware
- Improperly torqued HO2S
- Restrictions-Refer to Restricted Exhaust .
- If a condition is found, repair the exhaust system.
Inspect the post catalyst HO2S for the following conditions:
- A grounded or damaged wiring harness
- Damaged sensor
- If a condition is found, replace the post catalyst HO2S.
If all physical conditions test normal, test or replace the catalytic converter.