Code 25: Mat Sensor Temp High: Notes

The ECM applies and monitors a voltage signal (4-6 volts) to MAT sensor. 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 sensor terminals with harness disconnected.

1. This checks if the code is a hard failure or an intermittent condition. Code 25 will set if a MAT temperature greater than 275°F (135°C) is sensed for more than 2 seconds.