Test Description

WARNING: This page is about a different car, the 2002 Oldsmobile Bravada, 2002 GMC Envoy XL, 2002 GMC Envoy, and 2002 Chevrolet TrailBlazer. However, it is still accessible from the selected car via links, so may be relevant.

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

2

Allow the engine to cool before performing this test. This allows the HO2S to cool which causes the HO2S signal voltage to return to near bias voltage, approximately 450 mV. This test determines if ground is constantly being applied to the HO2S heater.

3

After the HO2S heater is commanded ON, the HO2S will heat up. This will cause the signal voltage to change either more than or less than bias voltage, verifying the HO2S heater is operating.

4

This step tests for voltage at the HO2S heater. The O2 fuse supplies power to the HO2S heater.

5

This step verifies that the PCM is providing ground to the HO2S heater.

6

This step tests if ground is constantly being applied to the HO2S heater.

11

If more than one HO2S DTC is set, this is a good indication that the O2 fuse is open. Test all related circuits going to all the heated oxygen sensors for a short to ground. If you cannot locate a shorted circuit, it may be necessary to disconnect each HO2S one at a time to locate a shorted sensor.