Circuit/System Testing

Ignition ON, observe the TP Sensor percentage parameter with a scan tool. The throttle position (TP) sensor should be within 2-10 percent.
- If the TP sensor is not within the specified range, refer to DTC P0121, P0122, P0123, P0222, or P0223 (w/o Throttle Actuator Control) for further diagnosis.
Compare the MAP sensor parameter on the scan tool to the barometric pressure table. Refer to Altitude vs Barometric Pressure .
- If the manifold absolute pressure (MAP) sensor does not display the correct barometric pressure refer to DTC P0106 for further diagnosis.
Ignition OFF, disconnect the harness connector of the appropriate HO2S.
Ignition ON, verify that the HO2S parameter is between 350-500 mV.
- If less than 350 mV, test the signal circuit of the HO2S sensor for a short to ground. If the circuit/connections test normal, replace the engine control module (ECM).
Verify that none of the following conditions exist:
- Lean fuel injectors-Refer to Fuel Injector Balance Test with Special Tool .
- 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 (w/o Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (w/Special tool) .
- Exhaust leaks near the HO2S
- Contaminated HO2S - Silicon
- Engine vacuum leaks
- If you find any of the above conditions, repair as necessary.
If all circuits/connections test normal, replace the applicable HO2S.