Test Description

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

1. 4
   
   This step ensures that the ignition 1 voltage circuit to HO2S is not open or shorted. The test light should be connected to a good chassis ground, in case the HO2S low reference or HO2S heater low control circuit is malfunctioning.
2. 5
   
   This step checks the HO2S heater low control circuit. The engine must be running for PCM to enable the heater.
3. 6
   
   This step checks for a short to ground in HO2S heater low control circuit.
4. 7
   
   This step checks for a short to voltage on HO2S heater low control circuit.