Circuit Description

The Heated Oxygen Sensor No. 2 (HO2S2) activity is constantly monitored by PCM. When sensor reaches about 600°F (318°C), it responds to oxygen content in the exhaust. PCM produces a bias voltage of about 450 millivolts on sensor circuit. When sensor is cold, resistance is extremely high (open circuit), and as sensor warms up, internal resistance decreases. When sensor temperature reaches about 600°F (318°C), it starts producing a voltage based on oxygen content in exhaust system. This voltage is used by PCM to determine a rich or lean oxygen sensor signal and adjusts the fuel mixture accordingly.

DTC will set if HO2S2 voltage is greater than 1042 mV for 50 seconds when:

• DTC P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0171, P0201, P0202, P0203, P0204, P0300, P0301, P0302, P0303, P0304, P0336, P0440, P0442, P0446, P0506, P0507, P0601, P0602 or P1441 not set.
• ECT greater than 104°F (40°C) for 140 seconds.
• TP angle between 8-56 percent.
• Air flow greater than 5.5 gm/s for 140 seconds.