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

IAT Sensor:

Description

Notice: Numbers in text correspond to numbered components in image.

The Intake Air Temperature (IAT) sensor is a grommet (1) which contains a semiconductor device which changes the resistance based on temperature (a thermistor). The IAT sensor is in the air intake passage of the engine air induction system. The IAT sensor has a signal circuit and a ground circuit. The ECM applies a voltage (about 5.0 volts) on the signal circuit to the sensor. The ECM monitors changes in this voltage that are caused by the changes in the resistance of the sensor in order to determine the intake air temperature.

Operation

When the intake air is cold, the sensor (thermistor) resistance is high, and the ECM's signal voltage is only pulled down a small amount through the sensor to ground. Therefore, the ECM will sense a high signal voltage (low temperature). When the intake air is warm, the sensor resistance is low, and the signal voltage is pulled down a greater amount. This causes the ECM to sense a low signal voltage (high temperature).

Scan Tool Diagnosis

The scan tool displays temperature of the air entering the engine, which should read close to ambient air temperature when engine is cold. The temperature should rise as underhood temperature increases. If the engine has not been run for several hours (overnight) the IAT sensor temperature and engine coolant temperature should read close to each other. If the ECM detects a malfunction in the IAT sensor circuit, the DTC P0110 - IAT Sensor Circuit will set.