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: O2 Sensor Lean Fuel Mixture (Heated Sensor Only): Notes
The ECM supplies a voltage of approximately .45 volt between ECM terminals D6 and D7 (if measurement is taken with a 10-megohm DVOM, reading may be as low as .32 volt). The O2 sensor varies voltage within a range of approximately one volt if exhaust is rich and down to about .10 volt if exhaust is lean. When sensor temperature is less than 600°F (316°C), the sensor acts like an open circuit and will not produce voltage. An open sensor circuit or cold sensor will cause an open loop condition.
- Code 44 will set under following conditions:
- Coolant temperature is greater than 158°F (70°C).
- Engine running for more than 50 seconds.
- Integrator count is not at 128.
- No Code 21A, 21B, 33A, or 33B is set.
- Oxygen sensor voltage is below .278 mV for 99 seconds.
- System is in closed loop.
- TPS is greater than 3 percent.
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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.