The Intake Air Temperature (IAT) sensor detects the temperature of the incoming air stream in a car machine. The IAT sensor resistance changes in response to the intake air temperature. The AIT is usually located in an intake air passage which is connected to the THA terminal on the ECM, it is used for detecting ambient temperature on a cold start and intake air temperature as the engine heats up the incoming air. The sensor resistance decreases as the surrounding air temperature increases. This provides a signal to the PCM, indicating the temperature of the incoming air charge. The following schematic shows the Typical Intake Air Temperature (IAT) Sensor Circuit Diagram.