Test Description

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

1. 2
   
   The HO2S 1 should be allowed to cool before performing this test. The HO2S 1 is cool enough if the voltage output is stable at bias or, about 450 millivolts. If the HO2S 1 heater is functioning, the signal voltage will gradually decrease as the sensor element warms. If the heater is not functioning, the HO2S 1 signal will remain near the 450 millivolts bias voltage.
2. 4
   
   This step ensures that the ignition 1 voltage circuit to the HO2S 1 is not open or shorted. The test light must be connected to a good ground, independent of the HO2S system.
3. 6
   
   This test must not be performed until the HO2S 1 heater has cooled and stabilized for at least 15 minutes. Heater resistance is typically about 5 ohms at room temperature.