Powertrain Controls - ECM/PCM

Diagnostic Chart:

Circuit Schematic:

Temperature - Resistance Chart For Sensors:

IAT CIRCUIT-TEMPERATURE OUT OF RANGE HIGH
The inlet air temperature (IAT) sensor is a thermistor located in the air intake passage of the air induction system on the engine. When the sensor is cold it has a high resistance; the resistance decreases as the temperature of the sensor increases. The PCM supplies a five volt signal to the sensor which is also connected to ground. The PCM reads the voltage drop on the sensor signal line to determine air temperature.

DTC PARAMETERS

DTC 25 will set if:
^ The IAT reading is over 125°C (257°F).

DIAGNOSTIC AIDS
Refer to Temperature vs. Resistance chart.

When attempting to diagnose an intermittent problem, use the Scan tool[1] to review supplemental diagnostic information. The supplemental data can be used to duplicate a problem.

Check the tightness of the female terminal grip with a spare male terminal.

IAT temperature may be compared to ECT temperature with a Scan tool if engine has cooled overnight at ambient temperature. They should be within four degrees of each other with ignition On and engine Off.

[1]Select Malfunction History from Scan tool Engine Control (EC) menu.