Circuit/System Testing
WARNING: This page is about a different car, the 2012 GMC Yukon, 2012 Chevrolet Tahoe, and 2012 Cadillac Escalade. However, it is still accessible from the selected car via links, so may be relevant.
- Ignition OFF, open the hood to disable the Auto-Stop function.
- Disconnect the harness connector at the appropriate HO2S.
- Ignition OFF and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 5 Ω between the low reference circuit terminal A and ground.
- If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
- Ignition ON, verify the appropriate scan tool HO2S parameter is approximately 450 mV.
- If less than the specified value, test the signal circuit for a short to ground. If the circuit tests normal, replace the ECM.
- If greater than the specified value, test the signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.
- Ignition ON, install a 3 A fused jumper wire between the signal circuit terminal B and ground. Verify the scan tool HO2S parameter is less than 60 mV.
- If greater than the specified range, test the signal circuit for an open/high resistance. If the circuits test normal, replace the ECM.
- Verify none of the following conditions exist:
- Rich fuel injectors-Refer to Fuel Injector Diagnosis (CH47976) , Fuel Injector Diagnosis (J39021 or Scan Tool)
- Water intrusion in the HO2S harness connector
- High fuel system pressure-Refer to Fuel System Diagnosis (Without FPCM) , Fuel System Diagnosis (FPCM)
- Fuel that is contaminated-Refer to Alcohol/Contaminants-in-Fuel Diagnosis
- Fuel saturation of the evaporative emission (EVAP) canister
- If you find any of the above conditions, repair as necessary.
- If all circuits test normal, replace the appropriate HO2S.