The IAT (Intake Air Temperature) sensor is a thermistor that varies its resistance as a function of temperature. This sensor is sometimes integrated in the MAF sensor (Mass Air Flow Sensor) or is located in the air filter duct housing.
The PCM (Power Train Control Module) controls the air temperature entering the engine. The IAT sensor has 5 volts reference which is supplied by the PCM (Powertrain Control Module). Because the resistance of the IAT sensor changes according to the temperature, when the temperature raises, the resistance drops. If the temperature drops, there may be a high signal voltage. In the event that the Power Train Control Module observes that the signal voltage is above 5 volts, the fault code P0113 OBD2 is established.