DTC 25

MAT Sensor Circuit:

Code 25 Wiring Diagram:

CIRCUIT DESCRIPTION:

The Manifold Air Temperature (MAT) sensor uses a thermistor to control the signal voltage to the ECM. The ECM applies a voltage (5.0 volts) on GRAY wire to the sensor. When manifold air is cold, the sensor (thermistor) resistance is high, therefore, the ECM will see a high signal voltage. As the air warms, the sensor resistance becomes less, and the voltage drops.

TEST DESCRIPTION: Numbers below refer to circled numbers on the diagnostic chart.

1. Code 25 will set if:

^ Signal voltage indicates an air temperature greater than 136°C (277°F) for 2 seconds.

2. If the resistance is less than 100 OHM's, replace the sensor.

DIAGNOSTIC AIDS:

An intermittent may be caused by a poor connection rubbed through wire insulation or a wire broken inside the insulation. Inspect ECM harness connectors for backed out terminals "A13" or "A16," improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection and damaged harness.