Circuit Description

Oxygen Sensor No. 1 (O2S1) 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 O2S1 voltage is inactive (not reading greater than 399-499 mV) for 125 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.
• Engine running at least 30 seconds.
• ECT greater than 158°F (70°C) for 20 seconds.
• TP angle between 8-56 percent.
• Engine running for greater than 200 seconds.
• System in closed-loop.