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.

NOTE: All modules must be powered down or misdiagnosis may result.

Ignition OFF, disconnect the scan tool and wait 60 seconds to ensure all modules are powered down.
Ignition OFF, disconnect the harness connector at the appropriate HO2S.
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) or 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) or Fuel System Diagnosis (FPCM)
- Fuel that is contaminated-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (Special Tool)
- 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.