Circuit Description

PCM continuously monitors HO2S activity for 100 seconds. During this monitoring period, PCM counts the number of times that a rich to lean and lean to rich response is indicated and adds the amount of time it took in order to complete all transitions. With this information, an average time for each transition can be determined. If average response time is too slow, a DTC P0133 will be set. A lean to rich transition is indicated when HO2S voltage changes from less than 300 mV to more than 600 mV. A rich to lean transition is indicated when HO2S voltage changes from more than 600 mV to less than 300 mV. An HO2S that responds too slowly is likely to be inoperative and should be replaced.