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

OPERATION
The Intake Air Temperature (IAT) sensor is a thermistor (a resistor which changes value based on the temperature of air entering the engine), similar to the Engine Coolant Temperature (ECT) sensor. Low temperature produces a high resistance (1000,000 ohms at -40°C / -40°F) while high temperature causes low resistance (70 ohms at 130°C / 266°F). The Powertrain Control Module (PCM) supplies a 5 volt signal to the sensor through a resistor in the PCM and measures the terminal voltage. The voltage will be high when the intake air is cold, and low when the intake air is is hot. By measuring the voltage, the PCM knows the intake air temperature. This input is used in starting and running fuel control calculations.

A failure in the IAT sensor circuit should set either a Diagnostic Trouble Code (DTC) P0112 or P0113.