Code 25: Mat Sensor Temp. High (2.5L): 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 ECM sees 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.

Test Number 1)  This checks if the code is a hard failure or an intermittent condition. Code 25 will set if a VSS signal is present and MAT sensor temperature is greater than 302°F (150°C) is sensed for more than 2 seconds.