DTC 25

Fig. 012 - Chart - Code 25 Manifold Air Temperature (Signal Voltage Low):

Fig. 013 - WIRING DIAGRAM for Code 25 Manifold Air Temperature (Signal Voltage Low). VIN W:

CODE 25

MANIFOLD AIR TEMPERATURE(MAT) SENSOR

(SIGNAL VOLTAGE LOW)

2.8L "X" SERIES

FUEL INJECTION (PORT)

The Manifold Air Temperature Sensor uses a thermistor to control the signal-voltage to the ECM. The ECM applies a voltage (4-6) on CKT 996 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.
Code 25 will set if:
a. Signal voltage indicates a manifold air temperature greater than 135°C (275°F) for 3 seconds.
b. Time since engine start is 8 minutes or longer.
c. A vehicle speed is present.
Due to the conditions necessary to set a Code 25 the "SERVICE ENGINE SOON" light will only remain on while the signal is low and vehicle speed is present.
1. If voltage is above 4 volts, the ECM and wiring are OK.
2. If the resistance is less than 185 ohms replace the sensor.