Circuit Description

Heated Oxygen Sensor (HO2S) No. 1 produces a voltage that varies within a range of 100-900 millivolts under normal operating conditions. PCM monitors this voltage and determines if exhaust is lean or rich. If input voltage is low, exhaust is lean. If input voltage is high, exhaust is rich. PCM constantly monitors HO2S No. 1 signal during closed-loop operation and compensates for a rich or lean condition by decreasing or increasing injector pulse width as necessary. If HO2S No. 1 voltage remains excessively low or near 450 millivolts for an extended period of time, DTC will set.