Code P043, Front Oxygen Sensor Signal Rich: Notes

PCM provides a .45-volt reference signal to oxygen sensor on circuit No. 412. When oxygen sensor temperature is less than 392°F (200°C), sensor signal voltage will be about .45 volt and PCM will keep system in open loop operation. When oxygen sensor temperature is greater than 392°F (200°C), sensor will rapidly swing from rich to lean, at least one swing every 2 seconds, if PCM is in good control of the air/fuel mixture.

Code P043 is designed to set if oxygen sensor voltage stays rich for more than 50.3 seconds during test conditions. Code P043 also sets when an oxygen sensor circuit fault exists giving a false rich indication, or when air/fuel ratio is actually rich due to a fuel control or emission system fault.