Intake Air Temperature Sensor
WARNING: This page is about a different car, the 2003 Cadillac CTS. However, it is still accessible from the selected car via links, so may be relevant.
The Intake Air Temperature (IAT) sensor is a variable resistor. The IAT sensor has a signal circuit and a low reference circuit. The IAT sensor measures the temperature of the air entering the engine. The ECM supplies 5 volts to the IAT signal circuit, and a ground for the IAT low reference circuit. When IAT sensor is cold, sensor resistance is high. When the air temperature increases, sensor resistance decreases. With high sensor resistance, the ECM detects a high voltage on the IAT sensor signal circuit. With lower sensor resistance, the ECM detects a lower voltage on the IAT sensor signal circuit. If ECM detects an excessively low IAT sensor signal voltage, indicating a high temperature, DTC will set.