Intake Air Temperature Sensor

The Intake Air Temperature (IAT) sensor is a thermistor (temperature sensitive resistor) mounted in the fresh air intake tube. See Figure . Low intake air temperature produces high internal sensor resistance, while high temperature causes low internal sensor resistance. The PCM supplies and monitors a 5-volt signal to sensor through a pull-down resistor in PCM.

IAT sensor allows PCM to determine intake air temperature. If intake air temperature becomes excessively high, PCM compensates by slightly retarding ignition timing. After a vehicle has cooled overnight, IAT and ECT sensor signals (resistance and temperature) should be close to the same reading. Failure in IAT sensor circuit should set a related DTC. To diagnose, see SELF-DIAGNOSTICS - 4.2L BRAVADA, ENVOY, ENVOY XL, TRAILBLAZER & TRAILBLAZER EXT article.