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 23, Manifold Air Temperature (Mat) Sensor Circuit High Temperature Indicated
MAT sensor uses a thermistor to control signal voltage to the ECM. The ECM applies 4-6 volts on circuit No. 472 to the sensor. When manifold air is cold, sensor resistance is high, this means ECM will see high signal voltage. As air temperature warms, sensor resistance becomes less and voltage drops.
- Code 23 will set if signal voltage indicates manifold air temperature is more than 302°F (150°C) for 2 seconds.
- If resistance is less than 100 ohms, replace sensor.
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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.