Monitor Description

The heated oxygen sensor generates waveform of a voltage between 0 V and 1 V in response to the oxygen concentration in the exhaust gases. When the output voltage of the heated oxygen sensor is 0.55 V or more, the ECM judges that the air-fuel ratio is RICH. When it is 0.40 V or less, the ECM judges that the air-fuel ratio is LEAN.

If the rear heated oxygen sensor output dose not change between RICH and LEAN during "Stop and GO" driving, the ECM interprets this as malfunction in the sensor and sets a DTC. Also, if the sensor output remains at less than 0.05 V for more than 126 seconds (when ECM monitored the sensor for 210 seconds while the air-fuel feed back is being performed), the ECM will interpret this as a fault. In either case, the ECM will turn on the MIL and set a DTC.