DTC 25

Code 25 Chart:

Manifold Air Temperature Sensor Wiring Diagram:

CIRCUIT DESCRIPTION:

The Manifold Air Temperature (MAT) sensor uses a thermistor to control the signal voltage at the ECM. The ECM applies a voltage (4-6 volts) on circuit 472 to the sensor. When the air is cold, the sensor (thermistor) resistance is high, therefore, the ECM will see a high signal voltage. If the air is warm, the sensor resistance is low, therefore, the ECM will see a low voltage.

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

1. A Code 25 will set, due to an open sensor, wire, or connection. This test will determine if the wiring and ECM are OK. A Code 25 will set if:

a. A signal voltage indicates a manifold air temperature below -35°C (-31°F)
b. Time since engine start is 1 minute or longer.
c. No Vehicle Speed Sensor (VSS) signal.

2. If the resistance is greater than 25,000 OHMS, replace the sensor.