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

A Tech 1 scan tool displays the temperature of the air entering into the engine. This should be close to ambient air temperature when the engine is cold, and rise as underhood temperatures increase. If the engine has not run for several hours (overnight), the scan Intake Air Temperature (IAT) sensor temperature and coolant temperature should be close to each other. A fault in the IAT sensor circuit will set a Diagnostic Trouble Code (DTC) 23 IAT Sensor (Low Temp) or DTC 25 IAT Sensor (High Temp). The DTC charts also contain a chart to check for sensor resistance values relative to temperature.