Test Description

The numbers below refer to the step numbers in the diagnostic procedures.

1. 2
   
   The HO2S 1 voltage may default to the bias voltage. The DTC should be cleared and the Freeze Frame/Failure Records data recorded before proceeding. A normally functioning HO2S 1 voltage signal will fluctuate above and below the bias voltage amount.
2. 4
   
   A voltage reading other than the specified amount in this step indicates an open circuit condition in the high signal circuit or the PCM.
3. 6
   
   This step checks the HO2S 1 signal circuits from the HO2S connector and the PCM connectors, including the low reference loop between the PCM connectors.
4. 8
   
   This step checks for correct HO2S 1 heater circuit operation up to the HO2S connector. The heater low control is controlled by the PCM. The engine must be running to enable the HO2S heater.
5. 9
   
   The conditions listed in the table may contribute to the failure of the HO2S. The conditions listed apply only to this type of failure.