Circuit/System Description

The intake air temperature (IAT) sensor 2 is a variable resistor. The IAT 2 sensor measures the temperature of the air at the engine intake manifold. The engine control module (ECM) supplies 5 volts to the IAT 2 signal circuit, and a ground for the IAT 2 low reference circuit. When the IAT 2 sensor is cold, the sensor resistance is high. When the intake manifold air temperature increases, the sensor resistance decreases. With high sensor resistance, the ECM detects a high voltage on the IAT 2 signal circuit. With lower sensor resistance, the ECM detects a lower voltage on the IAT 2 signal circuit. The ECM monitors the IAT 2 and the IAT signal voltages for a signal voltage that is not within a calibrated range of each other.