The Intake Air Temperature (IAT) sensor is located inside of the volume air flow sensor box, attached between the air cleaner assembly and the air intake hose. The IAT functions by converting the temperature of the intake air into voltage, which is then fed to the ECM. The IAT sensor does this by taking the 5 volt power current, which is made by resistance inside the ECM, and grounding it back to the ECM. Before the current is grounded it passes through the IAT sensor, which is also a form of resistor, and is reduced by the resistance at an inverse proportion to the intake air temperature. In other words, the higher the intake air temperature, the lower the resistance of the IAT sensor. The ECM, based upon these signals from the IAT sensor, then corrects the amount of fuel injection and ignition timing.
NOTE: Since the air temperature is measured after the air cleaner, the air has some chance to warm up. Therefore, the IAT sensor indicates a different temperature than the outside temperature.