Circuit Description

WARNING: This page is about a different car, the 2002 Isuzu Trooper. However, it is still accessible from the selected car via links, so may be relevant.

PCM continuously monitors HO2S activity for 90 seconds after closed loop has been enabled. During monitoring period, PCM counts number of times that a rich-to-lean and lean-to-rich response is indicated and adds the amount of time it took to complete all rich-to-lean and lean-to-rich transitions. With this information, an average time for lean-to-rich and rich-to-lean transitions can be determined. If the average response time of either transition is too slow, a DTC P0133 will set. A lean-to-rich transition is indicated when HO2S voltage changes from less than 300 millivolts to more than 600 millivolts. A rich-to-lean transition is indicated when HO2S voltage changes from more than 600 millivolts to less than 300 millivolts. An HO2S that responds too slowly is likely to be faulty and should be replaced.

When DTC sets, PCM illuminates MIL on second trip after fault was detected. PCM will store conditions present when DTC was set as freeze frame data in the FAILURE RECORDS data. Vehicle will operate in Open Loop mode only.

PCM will turn MIL off on third consecutive trip cycle during which diagnostic runs and fault is no longer recognized. A history DTC P0133 will clear after 40 consecutive trip cycles during which diagnostic runs and fault is no longer recognized. DTC can be cleared with scan tool, or by disconnecting battery voltage feed to PCM.