Oxygen Sensor: Description and Operation

PURPOSE
The exhaust Heated Oxygen Sensor (HO2S) is mounted in the exhaust system where it can monitor the oxygen content of the exhaust gas stream. By monitoring the voltage output of the oxygen sensor, the Powertrain Control Module (PCM) calculates what fuel mixture command to give to the injector (lean mixture-low HO2S voltage = rich command, rich mixture-high HO2S voltage = lean command).

OPERATION
The oxygen content in the exhaust reacts with the sensor to produce voltage output. This voltage should constantly fluctuate from approximately 100 mV (high oxygen content - lean mixture) to 900 mV (low oxygen content - rich mixture). The heated oxygen sensor voltage can be monitored with a Tech 1.