Circuit/System Testing

Ignition OFF for 1 minute. 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 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 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 (W/J39021 or W/Tech 2) or Fuel Injector Diagnosis (W/CH47976)
- Water intrusion in the HO2S harness connector
- High fuel system pressure-Refer to Fuel System Diagnosis
- Fuel that is contaminated-Refer to Alcohol/Contaminants-in-Fuel Diagnosis
- Exhaust restrictions
- Contaminated HO2S - Silicon
- An engine mechanical condition-Symptoms - Engine Mechanical
- If you find any of the above conditions, repair as necessary.
If all circuits test normal, replace the appropriate HO2S.