Pcm Code E44, Oxygen (O2) Sensor Lean Exhaust Signal: Description

PCM provides a .45-volt reference signal to O2 sensor on circuit No. 412. When O2 sensor is cold, less than 392°F (200°C), O2 sensor signal voltage will be about .45 volt. PCM will keep system in "open loop" operation. When O2 sensor is warm, greater than 392°F (200°C), O2 sensor signal voltage will swing from rich to lean rapidly. At least one swing every 2 seconds will happen if PCM is in good control of air/fuel mixture.

When PCM sees O2 sensor is varying from cold voltage of .45 volt, it will send system into "closed loop" operation. In "closed loop" operation, PCM will adjust fuel delivery rate to engine based on O2 sensor readings.

Code E44 is designed to set if O2 sensor stays at lean voltage for more than 51 seconds during test conditions. Code E44 will set when an O2 sensor circuit fault giving a false lean indication exists or when air/fuel ratio is actually lean due to a vacuum leak or fuel control system fault.