DTC 25

Code 25 - Manifold Air Temp. (MAT) Sensor:

Wiring Diagram for Manifold Air Temp. (MAT) Sensor:

CODE 25 - MANIFOLD AIR TEMPERATURE SENSOR CIRCUIT (MAT) HIGH TEMPERATURE INDICATED

Circuit Description:


The Manifold Air Temperature (MAT) sensor uses a thermistor to control the signal voltage to the Electronic Control Module (ECM). The ECM applies a voltage (about 5 volts) on CKT 472 to the sensor. When manifold air is cold, the sensor (thermistor) resistance is high, therefore, the ECM will see a high signal voltage. If the air warms, the sensor resistance becomes less, and the voltage drops.


Test Description: Numbers below refer to circled numbers on the diagnostic chart.

Code 25 will set if:

^ Signal voltage indicates a manifold air temperature greater than 135~C (275~F).

^ The above requirement is met for at least 30 seconds. Due to the conditions necessary to set a Code 25, the "Service Engine Soon" (SES) light will only stay "ON" while the fault is present.


1. A "Scan" tool may not be used to diagnose this fault, due to the ECM transmitting "default" (substitute) values, while the fault is present. If voltage is above 4 volts, the ECM and wiring are OK.


2. If the resistance is greater than 100 ohms, replace the sensor.