Intake Air Temperature Sensor

The Intake Air Temperature (IAT) sensor is a thermistor, a resistor which changes value based on temperature of air entering engine. Low temperature produces a high resistance (100,000 ohms at -40° C/-40° F), while high temperature causes a low resistance (70 ohms at 130° C/266° F).

The powertrain control module (PCM)/engine control module (ECM) provides 5 volts to IAT sensor through a resistor in PCM/ECM and measures change in voltage to determine intake air temperature. The voltage will be high when manifold air is cold and low when air is hot. The PCM/ECM knows intake air temperature by measuring voltage. The IAT sensor is also used to control spark timing when intake air is cold. A failure in IAT sensor circuit sets a diagnostic trouble code P0112 or P0113.