Air Temperature Sensor ( Ambient / Intake ): Testing and Inspection

DIAGNOSIS
A Tech 1 scan tool displays temperature of the air entering the engine and should read close to ambient air temperature when engine is cold and rise as underhood temperature increases. If the engine has not been run for several hours (overnight) the Intake Air Temperature (IAT) and Engine Coolant Temperature (ECT) should read close to each other. A failure in the IAT sensor circuit should set a Diagnostic Trouble Code (DTC) 23 or 25. The DTC charts also contain a "Diagnostic Aid' chart to check for sensor resistance values relative to temperature.