Diagnostic Aids
WARNING: This page does not describe the selected car, but rather 11 other vehicles, including the 2002 GMC Yukon XL, 2002 GMC Yukon, 2002 GMC Sierra, 2002 GMC Cab & Chassis Sierra, and 2002 Chevrolet Tahoe. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:
Never solder the HO2S wires.
- A malfunctioning HO2S heater or heater circuit. With the ignition ON and the engine OFF, the HO2S voltage displayed on a scan tool should gradually drop to below 0.150 volt, indicating that the heater works properly. If not, disconnect the HO2S and connect a test lamp between the terminals "C" and "D". If the test lamp does not light, repair the open in the HO2S ground circuit or the HO2S ignition positive voltage circuit. If the test lamp lights, replace the HO2S.
- The intermittent test. Use a scan tool in order to monitor this HO2S signal voltage. Move the related connectors and the wiring harness with a warm engine running at part throttle in Closed Loop. If the failure is induced, the HO2S signal voltage reading changes from the normal fluctuating voltage above 600 mV and below 300 mV, to a fixed value around 450 mV. This may help to isolate the location of the malfunction.
An intermittent may be caused by any of the following conditions:
- A poor connection.
- Rubbed through wire insulation.
- A broken wire inside the insulation.