Air Temperature Sensor ( Ambient / Intake ): Description and Operation

Intake Air Temperature Sensor:

Intake Air Temperature Sensor Wiring Schematic:

PURPOSE
The Intake Air Temperature (IAT) sensor measures the temperature of the intake air in the air cleaner. The IAT is a thermistor (a resistor which changes value based on the temperature of air entering the engine) and is mounted in the air cleaner assembly.

OPERATION
Low intake air temperature produces a high IAT sensor resistance, while high intake air temperature produces a low resistance. The Powertrain Control Module (PCM) supplies a 5 volt signal to the sensor through a resistor in the PCM and measures the voltage. The measured voltage varies with the temperature of the intake air, due to the changing resistance of the sensor. By measuring the voltage, the PCM calculates the intake air temperature. The PCM uses this information to control spark timing, air / fuel ratio and delays Exhaust Gas Recirculation (EGR) when the intake air is cold.

NOTE: A failure in the IAT sensor circuit should set either a Diagnostic Trouble Code (DTC) 23 or DTC 25. Once a DTC is set, the PCM will use an artificial default value for IAT and some vehicle performance will return.