The intake air temperature (IAT) sensor is a
thermistor which changes value based on the
temperature of air entering the engine. A low
temperature produces a high resistance (100,000
ohms at -40°C/-40°F), while a high temperature
causes a low resistance (70 ohms at
The PCM supplies a 5.0 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 to adjust the spark timing according to the
incoming air density.
A common OBD2 computer trouble code is p0113.
Intake Air Temperature Sensors