Code P044, Rear Oxygen Sensor Lean Signal: Notes

WARNING: This page is about a different car, the 1995 Cadillac Eldorado. However, it is still accessible from the selected car via links, so may be relevant.

PCM provides a .45-volt reference signal to oxygen sensor on circuit No. 1670. 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 begin to generate a signal voltage. In a rich environment, signal voltage will be greater than .45 volt. In a lean environment, signal voltage will be less than .45 volt. If PCM is in good control of air/fuel mixture, mixture will change from rich to lean rapidly (at least one change every 2 seconds).

Code P044 sets if oxygen sensor stays at lean voltage for more than 50 seconds during test conditions. Code P044 also sets when oxygen sensor circuit fails or when air/fuel ratio is actually lean due to vacuum leak or fuel control system fault.