Intake Air Temperature Sensor

The Intake Air Temperature (IAT) sensor is a variable resistor. The IAT sensor has a signal circuit and a low reference circuit. The IAT sensor measures the temperature of the air entering the engine. The Engine Control Module (ECM) supplies 5 volts to the IAT signal circuit, and a ground for the IAT low reference circuit. When the IAT sensor is cold, the sensor resistance is high. When the air temperature increases, the sensor resistance decreases. With high sensor resistance, the ECM detects a high voltage on the IAT signal circuit. With lower sensor resistance, the ECM detects a lower voltage on the IAT signal circuit. If the ECM detects an excessively low IAT signal voltage, indicating a high temperature, DTC P0112 sets. If the ECM detects an excessively high IAT signal voltage, indicating a low temperature, DTC P0113 sets.

Intake air temperature should read close to ambient temperature with engine cold, and rise as underhood temperature increases. After a vehicle has been parked overnight, IAT and ECT sensor signals (resistance and temperature) should be close to the same reading. Failure in IAT sensor circuit (open or short to ground) will cause monitored voltage to swing high or low and should set a related DTC.