Circuit/System Testing (w/LLT)
WARNING: This page is about a different car, the 2008 Cadillac CTS. However, it is still accessible from the selected car via links, so may be relevant.
- 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 (w/o Special Tool) .
- Exhaust leaks near the HO2S
- Contaminated HO2S - Silicon
- Engine vacuum leaks
- If you find any of the above conditions, repair as necessary.
- Ignition OFF, disconnect the harness connector at the appropriate HO2S 2.
- Ignition ON, verify the appropriate scan tool HO2S 2 voltage parameter is between 350-550 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.
- Connect the harness connector at the HO2S 2.
- Engine idling, raise the engine speed above 1,200 RPM for 30 seconds. Verify the appropriate scan tool HO2S 2 voltage parameter is greater than 60 mV.
- If less than the specified value, replace the HO2S 2.
- Engine idling, move the appropriate HO2S 1 and HO2S 2 harnesses between the HO2S harness connectors and the ECM. Observe the suspected scan tool HO2S 1 voltage parameter, and the HO2S 2 voltage parameter.
- If a parameter changes abruptly, repair the harness/connections as necessary.
- If all circuits/connections test normal, replace the applicable HO2S 1.