Test Description

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

1. 2
   
   The HO2S should be allowed to cool before performing this test. If the HO2S heater is functioning, the signal voltage will gradually increase or decrease as the sensor element warms. If the heater is not functioning, the HO2S signal will remain near the 450 mv bias voltage.
2. 4
   
   This step ensures that the ignition 1 voltage circuit to the HO2S is not open or shorted. The test lamp should be connected to a good ground, in case the HO2S low signal or HO2S heater ground circuit is poor.
3. 5
   
   This step tests the HO2S heater ground circuit.
4. 6
   
   This step checks for an open or shorted HO2S heater element. The heater element resistance will vary according to HO2S temperature. A hot HO2S heater element will measure a much higher resistance than a HO2S heater element at room temperature. Allow the HO2S to cool before measuring the HO2S heater element resistance.