Intake Air Temperature Sensor

The intake air temperature (IAT) sensor (3) is a thermistor which changes value based on the temperature of air entering the engine. A low air temperature produces a high resistance (100,000 Ohm at -40°C/-40°F), while a high air temperature causes low resistance (70 Ohm 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 read close to the ambient air temperature when engine is cold, and rise as underhood temperature increases. If the engine has not been run for several hours (overnight) the IAT and the ECT should read close to each other. A failure in the IAT sensor circuit should set DTC P0112 or DTC P0113.