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 25 - Mat Sensor Temperature High: Notes
The MAT sensor uses a thermistor to control the voltage signal to the ECM. The ECM applies and monitors a voltage signal (4-6 volts) to circuit No. 472. When manifold air is cold, the sensor resistance is high and the ECM will see a high signal voltage. As air warms, resistance decreases and voltage sensed by the ECM drops. Sensor resistance can be measured at ECM terminals "B5" and "W14".
Code 25 will set if a MAT temperature greater than 275°F (135°C) is sensed for more than 2 seconds. A Code 25 will also result if circuit No. 472 is shorted to ground.
- This test checks to determine if the code is a hard failure or an intermittent 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.
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