Circuit/System Testing

WARNING: This page is about a different car, the 2009 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.

Ignition OFF, open the hood to disable the Auto-Stop function.
Ignition ON, verify the scan tool hood position parameter displays Open.
- If the hood position does not display Open, refer to DTC P254F .
Engine operating, move the related HO2S harnesses for the appropriate rear sensor between the HO2S harness connector and the engine control module (ECM) while monitoring the appropriate HO2S voltage parameter. Verify that the HO2S parameter does not change abruptly while moving the related harnesses.
- If the HO2S parameter does change abruptly while moving the related harnesses repair the circuit as necessary.
Ignition OFF, disconnect the harness connector at the appropriate HO2S.
Ignition ON, verify that the HO2S parameter is between 350-500 mV.
- If less than the specified range, test the signal circuit for a short to ground. If the circuit/connections test normal, replace the ECM.
Verify that none of the following conditions exist:
- Lean condition
- Water intrusion in the HO2S harness connector
- Low 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 (without Special Tool)
- The vacuum hoses for splits, kinks, and proper connection
- The air intake system after the mass air flow (MAF) sensor for vacuum leaks
- Exhaust system leaks
- Contaminated HO2S - Silicon
- An engine mechanical condition-Refer to Symptoms - Engine Mechanical
- If you find any of the above conditions, repair as necessary.
If all circuits/connections test normal, replace the HO2S.