Circuit/System Testing

Ignition OFF, disconnect the harness connector at the appropriate HO2S.
Ignition ON, verify that the scan tool HO2S 1 voltage parameter is between 350-500 mV.
- If less than the specified range, test the signal circuit terminal B for a short to ground. If the circuit/connections test normal, replace the ECM.
- If greater than the specified range, test the signal circuit terminal B for a short to voltage. If the circuit/connections test normal, replace the ECM.
Install a 3 A fused jumper wire between the signal circuit terminal B and ground. Verify the scan tool HO2S 1 voltage parameter is less than 60 mV.
- If greater than the specified range, test the signal circuit for an open/high resistance. If the circuit/connections test normal, replace the ECM.
Connect a 3 A fused jumper wire between the signal circuit terminal B and the low reference circuit terminal A. Verify the scan tool HO2S 1 voltage parameter is less than 60 mV.
- If greater than the specified range, test the low reference circuit for an open/high resistance or for a short to voltage. If the circuit/connections test normal, replace the ECM.
Verify that the following conditions do not exist:
- Leaking fuel injectors.
- High fuel system pressure-Refer to Fuel System Diagnosis .
- Fuel that is contaminated-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (with Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (w/o Special Tool) .
- Restricted exhaust.
- If you find any of the above conditions, repair as necessary.
If all circuits/connections test normal, replace the appropriate HO2S 1.