Circuit/System Verification

Ignition ON, observe the scan tool DTC information. Verify there is no other HO2S or fuel trim DTC set.
- If any other HO2S or fuel trim DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .
Verify that none of the following conditions exist:
- Exhaust system leaks - Refer to Exhaust Leakage
- Engine vacuum leaks
- Low fuel system pressure - Refer to Fuel System Diagnosis .
- Fuel that is contaminated - Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
- Lean fuel injectors - Refer to Fuel Injector Solenoid Coil Test .
- If you find any of the above conditions, repair as necessary.

WARNING: Refer to Road Test Warning .

NOTE: A road load condition is necessary to obtain closed loop.

Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.