Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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