Circuit Description

When Oxygen Sensor (O2S) temperature reaches about 600°F (316°C), it becomes an electrical source that responds to the oxygen content in the exhaust. PCM produces a bias voltage of about 450 mV on the oxygen sensor circuit. When sensor is cold, its internal resistance is extremely high, therefore the PCM recognizes the bias as an open circuit. As the sensor warms up, the internal resistance decreases. When sensor reaches about 600°F (316°C), it starts producing a voltage based on the oxygen content in the exhaust stream. This voltage is used by the PCM to determine a rich or lean oxygen sensor signal and adjusts the fuel mixture accordingly.

DTC will set if O2S voltage is inactive (not reading outside 391-491 mV), engine has been running for at least one minute, TP sensor reads greater than 6.5 percent (off idle), no other engine sensor or misfire DTC(s) have been set or when commanded air/fuel ration is about 14.7:1. O2S signal is continuously monitored once these conditions are met.