Circuit/System Testing

Engine idling, raise the engine speed to greater than 1,200 RPM for greater than 30 seconds. Observe the scan tool HO2S 2 voltage parameter. Verify the parameter is less than 1,050 mV.
- If greater than the specified range, test the HO2S 2 high signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.
Move the related HO2S 2 harnesses between the HO2S harness connector and the engine control module (ECM). Observe the scan tool HO2S 2 voltage parameter. Verify the parameter does not change abruptly.
- If the parameter changes abruptly, repair the harness as necessary.
Verify that none of the following conditions exist:
- Collapsed air intake duct
- Restricted air filter element
- Mass air flow (MAF) sensor for foreign objects
- 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 fuel system pressure-Refer to Fuel System Diagnosis
- Fuel that is contaminated-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (w/o Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (w/ Special Tool)
- Exhaust leaks near the HO2S-Refer to Exhaust Leakage
- Excessive fuel in the crankcase. Change the oil as necessary
- If you find any of the above conditions, repair as necessary.
If all conditions test normal, replace the HO2S 2.