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 - Lean Exhaust Indication: Notes
The ECM supplies a voltage of about .45 volts between circuits No. 412 and 413. The O2 sensor varies that voltage from one volt (rich exhaust) to .10 volts (lean exhaust). The sensor acts like an open sensor circuit and produces no voltage when exhaust temperature is below 600°F (316°C). An open sensor circuit or cold sensor causes open loop operation.
Code 44 is set when O2 sensor signal at ECM is below .2 volts for 50 seconds or more and time since engine start is one minute or longer. Code 44 may also be set by any of the following conditions: circuit No. 413 open (circuit No. 412 voltage will be over one volt), low fuel pressure (see appropriate CHART A7 - FUEL SYSTEM DIAGNOSIS), fuel contamination, EGR stuck open or malfunctioning MAP sensor.
- Test checks to see if O2 sensor is registering a lean condition.
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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.