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 0.5 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 a malfunction in the rear heated oxygen sensor and sets a DTC. Also, if the sensor output remains at less than 0.05 V for more than 156 seconds when the ECM monitored the heated oxygen sensor for 260 seconds while the air fuel feedback is being performed (the detecting condition differs depending on the type of vehicles), the ECM will interpret this as a fault. In either case, the ECM will turn on the MIL and set a DTC.