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

Intake Air Temperature Sensor:

The Intake Air Temperature (IAT) sensor is a thermistor which changes value based upon the temperature of air entering the engine. A low temperature produces a high resistance of 100,700 ohms at -40°C (-40°F), while a high temperature causes a low resistance of 70 ohms at 130°C (266°F). The PCM supplies a 5 volt signal to the sensor through a resistor in the PCM and measures the voltage. The voltage is 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 to adjust the spark timing according to the incoming air density. The scan tool displays the temperature of the air entering the engine, which should be 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 ECT should be close to each other. A failure in the IAT sensor circuit should set DTC P0112 or DTC P0113.