The intake air temperature sensor, or IAT, in a Subaru measures the temperature of the outside air as it goes into the vehicle's air duct. It sends a signal to the computer so that the computer can adjust the air-to-fuel ratio in the engine, for the best engine performance and gas mileage. If the air intake sensor is not working properly, the computer sends a code, which illuminates the check engine light on the dash. Gas mileage will suffer, as will engine performance.
Open the hood.
Locate the intake air hose, which comes out of the air cleaner assembly.
Follow the hose to the intake air sensor. If the Subaru's engine is a double overhead cam engine, the intake air sensor is combined with the mass air flow sensor, which is also located in the air intake duct.
