Circuit/System Testing

Verify none of the following conditions exist:
- An exhaust leak near the HO2S-Refer to Symptoms - Engine Exhaust .
- Lean or rich fuel injectors-Refer to Fuel Injector Balance Test with Special Tool .
- The HO2S is not securely installed.
- Water intrusion or corrosion in the HO2S harness connector
- Poor terminal tension at the HO2S and at the ECM.
- HO2S wiring harness damage
- Low or high fuel system pressure-Refer to Fuel System Diagnosis .
- Fuel that is contaminated-Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
- Fuel saturation of the EVAP canister
- Engine vacuum leaks
- Incorrect RTV sealant
- Engine oil consumption-Refer to Symptoms - Engine Mechanical .
- Engine coolant consumption-Refer to Loss of Coolant .
- If you find any of the above conditions, repair as necessary.
Ignition OFF, disconnect the harness connector at the heated oxygen sensor (HO2S) 2.
Ignition ON, test for less than 0.1 volt between the low reference circuit terminal 1 and ground.
- If greater than the specified range, test the low reference circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.
Install a 3A fused jumper wire between the signal circuit terminal 4 and the low reference circuit terminal 1. Verify the appropriate HO2S parameter is less than 60 mV.
- If greater than the specified range, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
If all circuits test normal, test or replace the HO2S.