Code 44, Oxygen (O2) Sensor Circuit Lean Exhaust Indication): Notes

The ECM supplies a voltage of about .45 volt between terminals D7 and D6. If measured with 10-megohm voltmeter, this may read as low as .32 volt.

The oxygen sensor varies the voltage within a range of about one volt, if the exhaust is rich, down to about .10 volt if the exhaust is lean. The sensor is like an open circuit and produces no voltage when sensor temperature is less than 600°F (316°C). An open sensor circuit or cold sensor causes open loop operation.

Code 44 is set when the Oxygen (O2) sensor signal voltage on circuit No. 412 remains less than .3 volt for about one minute, and the system is operating in closed loop.