Circuit Description

The powertrain control module (PCM)/engine control module (ECM) monitors Oxygen Sensor (02S1) activity for 60 seconds after closed loop and stoichiometric operation have been established. During monitoring period PCM/ECM counts number of times that 02S l responds from rich-to-lean and adds amount of time it took to complete all transitions. With this information an average time for all transitions can be determined. The PCM/ECM then divides rich-to-lean average by lean-to-rich average to obtain a ratio. If O2S1 transition time ratio is not within this range. DTC P1134 will be set. indicating that 02S1 is not responding as expected to changes in exhaust oxygen content.