Test Description

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

1. 2
   
   This step checks for proper sensor activity. HO2S voltage should rapidly swing above and below the range specified.
2. 4
   
   This step checks the PCM and the high and low signal circuits between the PCM and the HO2S connector for proper operation.
3. 7
   
   This step checks for proper HO2S heater circuit operation up to the HO2S connector.
4. 8
   
   This step checks for proper circuit resistance between the HO2S low signal circuit and PCM ground.
5. 13
   
   This step checks for proper circuit resistance between the HO2S low signal circuit and PCM ground with a COLD sensor. A loose HO2S or poor thread to exhaust electrical contact will cause higher resistance when the HO2S is cold. Although 500 ohms is allowed, typical resistance should be less than 50 ohms.