Test Description
WARNING: This page does not describe the selected car, but rather 13 other vehicles, including the 2002 GMC Yukon XL, 2002 GMC Sierra, 2002 GMC Savana Special, 2002 GMC Savana Camper Special, and 2002 GMC Savana. However, it is still accessible from the selected car via links, so may be relevant.
The numbers below refer to the step numbers in the diagnostic procedures.
- 2
HO2S contamination is indicated if multiple response, switching, or time ratio HO2S DTCs are set. - 4
The use of leaded fuel may be indicated by the removal or tampering of the fuel filler restrictor. - 7
Even small exhaust leaks can cause slow response from the HO2S. - 12
An HO2S contaminated by silicone will have a white, powdery deposit on the portion of the HO2S that is exposed to the exhaust stream. The usual cause of silica contamination is the use of unapproved silicone RTV engine gasket material or the use of silicone based sprays or fluids within the engine. If the cause of this contamination is not corrected, the replacement HO2S will also get contaminated. - 13
If the voltage observed in step 8 is less than the range specified, a short between the HO2S high signal and low reference circuits or a short between the HO2S high signal circuit and ground is indicated. With the HO2S and the PCM disconnected, the resistance between the HO2S high signal and low reference circuits and the resistance between the HO2S high signal circuit and ground should measure infinite. If the voltage observed in step 8 is more than the range specified a short between the HO2S high signal circuit and an ignition voltage source is indicated. - 14
If the voltage observed in step 9 is not below the voltage specified, a high resistance, or open, in the HO2S high signal and low reference circuit is indicated. Good circuit continuity measures less than 5 ohms with the PCM and sensor disconnected. Measure between the PCM connector and the HO2S connector. Ensure that the PCM terminal contact is good.