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 CKT Lean Exhaust Indication: Notes
The ECM supplies a voltage of about .45 volt between terminals D7 and D6. If measured with 10-megohm voltmeter, voltage reading may be as low as .32 volt.
The oxygen sensor varies voltage within range of approximately .1 volt (lean exhaust) to 1.0 volt (rich exhaust). 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 oxygen (O2) sensor voltage on the signal wire remains less than .2 volt for about one minute, the system is operating in closed loop, and Code 33 or 34 is set.
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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.