Circuit/System Description

The intake air temperature (IAT) sensor 2 is a variable resistor. The IAT sensor 2 has a signal circuit and a low reference circuit. The IAT sensor measures the temperature of the air at the engines 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 sensor 2 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 continuously monitors the IAT signal voltage for an excessively high or low voltage, or a voltage signal that is not in correlation with the mass air flow (MAF)/IAT sensor.