Circuit/System Testing

Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the appropriate B52 HO2S. 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 B52 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 K20 ECM.
- If greater than the specified value, test the signal circuit for a short to voltage. If the circuit tests normal, replace the K20 ECM.
Install a 3 A fused jumper wire between the signal circuit terminal B and ground. Verify the scan tool B52 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 K20 ECM.
Verify none of the following conditions exist:
- Rich fuel at the injectors-Refer to Fuel Injector Diagnosis (CH47976) , Fuel Injector Diagnosis (J39021 or Scan Tool)
- Water intrusion in the B52 HO2S harness connector
- High fuel system pressure-Refer to Fuel System Diagnosis
- 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 B52 HO2S.