Circuit/System Verification
WARNING: This page is about a different variant/trim than selected.
- If any HO2S heater DTCs are set, perform those diagnostics first.
- Allow the engine to reach operating temperature.
- Engine running, observe the affected HO2S parameter with a scan tool.
- The pre-catalyst oxygen sensors value should vary from below 200 mV to above 800 mV and respond to fueling changes.
- The post-catalyst oxygen sensors value should change more than 200 mV when the throttle is quickly cycled 3 times from closed to wide open and back to closed after running the engine at 1,500 RPM for 30 seconds.
- The affected HO2S may be damaged due to contamination. Prior to replacing the affected HO2S, inspect for the following sources of contamination:
- A silicon contaminated HO2S
- Fuel contamination - Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
- Engine oil consumption - Refer to Oil Consumption Diagnosis .
- Engine coolant consumption - Refer to Cooling System Leak Testing .
CAUTION: Refer to Silicon Contamination of Heated Oxygen Sensors Caution .