Air Temperature Sensor ( Ambient / Intake ): Description and Operation

Intake Air Temperature (IAT) Sensor Circuit:

PURPOSE:
The Intake Air Temperature (IAT) sensor is a thermistor, a variable resistor which changes value based on temperature, mounted in the air cleaner assembly. The IAT sensor input affects fuel delivery and ignition timing controls in the PCM.

OPERATION:
The PCM supplies 5 volts to the IAT sensor and monitors the voltage on a signal line. The sensor provides a path to ground through its thermistor. The voltage will be high when the intake air is cold and low when the air is hot. By monitoring the voltage, the PCM calculates the intake air temperature.

Low intake air temperature produces high resistance, 100,000 ohms at -40°C (-40°F), while high temperature causes low resistance, 70 ohms at 130°C (266°F). A failure in the IAT circuit should set Diagnostic Trouble Codes (DTC) 23 or 25.