Intake Air Temperature (IAT) Sensor
The IAT sensor is integrated into the mass air flow (MAF) sensor. It is a thermistor device in which resistance changes with temperature. The electrical resistance of a thermistor decreases as the temperature increases, and the resistance increases as the temperature decreases. The varying resistance affects the voltage drop across the sensor terminals and provides electrical signals to the PCM corresponding to temperature.
A thermistor type sensor is considered a passive sensor. A passive sensor is connected to a voltage divider network so that varying the resistance of the passive sensor causes a variation in the total current flow.
Voltage that is dropped across a fixed resistor in a series with the sensor resistor determines the voltage signal at the PCM. This voltage signal is equal to the reference voltage minus the voltage drop across the fixed resistor.
The IAT sensor provides air temperature information to the PCM. The PCM uses the air temperature information as a correction factor in the calculation of fuel, and ignition timing.