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 response times are greater than 1199 milliseconds for rich-to-lean sweeps or lean-to-rich sweeps are greater than 600 milliseconds and when the following conditions have been met for 30 seconds:

• 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 167°F (75°C).
• Engine speed is 600-2400 RPM for M/T or 1800-2300 RPM for A/T.
• TP angle between 8-15 percent.
• EVAP purge is commanded to 80 percent or greater.
• Purge learned memory is greater than 220.
• Engine running for greater than 200 seconds.
• System in closed-loop.