Circuit/System Testing

Verify that none of the following conditions exist:
- Lean or rich fuel injectors - Refer to FUEL INJECTOR BALANCE TEST WITH SPECIAL TOOL or FUEL INJECTOR BALANCE TEST WITH TECH 2 .
- Water intrusion in the HO2S harness connector
- HO2S wiring harness damage
- Incorrect RTV sealant
- Low or high fuel system pressure - Refer to FUEL SYSTEM DIAGNOSIS .
- Fuel that is contaminated - Refer to ALCOHOL/CONTAMINANTS-IN-FUEL DIAGNOSIS (W/O SPECIAL TOOL) and ALCOHOL/CONTAMINANTS-IN-FUEL DIAGNOSIS (W/ SPECIAL TOOL) .
- Fuel saturation of the evaporative emission (EVAP) canister
- Exhaust leaks near the HO2S
- Engine vacuum leaks
- Engine oil consumption
- Engine coolant consumption
  - If you find any of the above conditions, repair as necessary.
If all conditions test normal, replace the appropriate HO2S.