Intake Air Temperature Sensor

The Intake Air Temperature (IAT) sensor is a thermistor (temperature sensitive resistor) mounted in the intake manifold. The PCM supplies and monitors a 5-volt signal to IAT sensor through a resistor in PCM. This monitored 5-volt signal is then reduced by resistance of the intake air temperature. Low intake air temperature produces high resistance, while high intake air temperature produces low resistance. By monitoring this voltage, PCM determines manifold air temperature. IAT sensor signal is used to make fuel control calculations according to incoming air density.

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. An IAT sensor which is out of calibration will not set a Diagnostic Trouble Code (DTC), but will cause fuel delivery and driveability problems. 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.