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

The Intake Air Temperature (IAT) sensor is a thermistor which changes value based on the temperature of air entering the engine. A low air temperature produces a high resistance, while a high temperature causes a low resistance. The PCM supplies a 5 volt signal to the sensor through a resistor in the PCM and measures the voltage. The voltage will be high when the incoming air is cold, and low when the air is hot. By measuring the voltage, the PCM calculates the incoming air temperature.

The IAT sensor signal is used in calculating the incoming air density. The scan tool displays the temperature of the air entering the engine, which should read close to the ambient air temperature when the engine is cold, and rise as the underhood temperature increases. If the engine has not been run for several hours or overnight the IAT and the engine coolant temperature should read close to each other. A failure in the IAT sensor circuit should set a DTC P0112 or DTC P0113.