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.

Ignition OFF, disconnect the harness connector at the appropriate HO2S 1.
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 for a short to ground. If the circuit/connections test normal, replace the ECM.
- If greater than the specified range, test the signal circuit for a short to voltage. If the circuit/connections test normal, replace the ECM.
Install a 3A fused jumper wire between the signal circuit terminal B and ground. Verify the HO2S 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 3A fused jumper wire between the signal circuit terminal B and the low reference circuit terminal A. Verify the HO2S 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:
- Lean condition.
- 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.
- Engine vacuum leaks.
- If you find any of the above conditions, repair as necessary.
If all circuits/connections test normal, replace the appropriate HO2S 1.