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. Low temperature produces a high resistance (100,000 ohms at -40°C/-40°F), while high temperature causes low resistance (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 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 (overnight) the IAT sensor temperature and the engine coolant temperature should read close to each other. A failure in the IAT sensor circuit should set DTC P0112 Intake Air Temperature (IAT)Sensor Circuit Low Voltage or DTC P0113 Intake Air Temperature (IAT) Sensor Circuit High Voltage.