Circuit Description

PCM provides a 5-volt reference signal to the oxygen sensor. When oxygen sensor is cold, sensor signal voltage will be about 5 volts and PCM will keep the system in "open loop" operation. When oxygen sensor is warm, 392°F (200°C), sensor will swing from rich to lean rapidly (one swing every 2 seconds), if PCM is in good control of air/fuel mixture. If oxygen is slow to respond to changes in exhaust oxygen content, DTC will set.