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

A "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 under hood temperature increases. If the engine has not been run for several hours (overnight), the IAT sensor temperature and ECT readings should be close to each other. A failure in the IAT sensor circuit should set a DTC 23. The DTC charts also contain a chart to check for sensor resistance values relative to temperature.