Test Description

The number below refer to the step number on the diagnostic procedure.

1. 2
   
   HO2S contamination is indicated if multiple response, switching, or time ratio HO2S DTCs are set.
2. 4
   
   The use of leaded fuel may be indicated by evidence of the removal or tampering of the fuel filter restrictor. 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 an unapproved 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 become contaminated.
3. 7
   
   Even small exhaust leaks can cause slow response from the HO2S.
4. 11
   
   If the voltage observed in step  9 is less than the range specified, a short between the high and low signal circuits or a short between the high signal circuit and ground is indicated. With the HO2S and the PCM disconnected the resistance between the high and low signal circuits and the resistance between the 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 high signal circuit and an ignition voltage source is indicated.
5. 12
   
   If the voltage observed in step  9 is not less than the voltage specified, a high resistance, or an open, high, or low signal circuit is indicated. A good circuit continuity measures less than 5 ohms with the PCM and sensor disconnected. Measure between the PCM connector and the HO2S 1 connector. Ensure that the PCM terminal contact is good.