Code 25 - Mat Sensor Temperature High: Notes

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".

1. Checks to determine 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.