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

Voltage Versus Temperature Chart:

The Intake Air Temperature (IAT) sensor is a thermistor integrated with the Mass Air Flow (MAF) sensor. The AT sensor resistance varies from 100,000 ohms at 40°C (40°F) to 70 ohms at 130°C (266°F). The PCM uses the IAT signal to calculate the intake air temperature. The PCM applies 5 volts to the IAT signal circuit through a pull-up resistor. When the intake temperature is cold, the IAT sensor resistance is high. This causes the PCM to detect a high AT signal voltage. As the underhood temperatures increase, the IAT sensor resistance lowers. The PCM should detect a low AT signal voltage.

The scan tool displays the intake air temperature in degrees. The IAT sensor display should read close to ambient air temperature when the engine is cold. As the underhood temperature increases, the IAT sensor display should also increase. If the engine has not been run for several hours (overnight), the IAT sensor and ECT sensor scan tool displays should read close to each other. A hard fault in the IAT sensor circuit should set DTC P0112 or P0113. An intermittent fault should set DTC P1111 or DTC P1112.

To check IAT sensor resistance relative to temperature, refer to the Temperature vs Resistance table. [1][2]Computers and Control Systems