Oxygen Sensor: Testing and Inspection

Circuit Description
The Generator Charging Circuit supplies Battery voltage to the Heater part of Heated Oxygen Sensor (HO2S). The Heater warms the HO2S to allow a varying voltage to be produced by the HO2S more rapidly instead of waiting for the HO2S to heat-up on its own.




Test Description
Number(s) below refer to circled number(s) on the diagnostic chart.

NOTE: The following test procedures are for the Heater part of the HO2S. No malfunction Diagnostic Trouble Codes (DTCs) will be logged if the Heater fails to function properly.

1. This will verify that Battery positive voltage is present for the Heater.
2. This check will test the ground Circuit to the Heater.
3. This tests the Heater Element resistance. Resistance will vary with the temperature of the Sensor. Normal resistance is between 3.5 - 14.3 ohms.

Diagnostic Aids
- A poor or loose connection at the HO2S could result in a false DTC being set or the O2 Heater not functioning properly.
- A shorted HO2S Heater could cause a DTC 13 to set.