Dirty air filter
Faulty Intake Air Temperature (IAT) sensor
Intake Air Temperature sensor harness is open or shorted
Intake Air Temperature sensor circuit poor electrical connection
Engine Light ON (or Service Engine Soon Warning Light)
This Diagnostic Trouble Code (DTC) is stored in the Engine Control Module (ECM) when the output from the Intake Air Temperature (IAT) sensor is not as expected or missing. The ECM uses information from the engine coolant temperature sensor and engine oil temperature sensor to carry out a plausibility check on the signal. The IAT sensors are normally negative temperature coefficient thermistors. The signal voltage drops as the intake air temperature increases. The intake air temperature sensor can be integrated into the Mass Air Flow (MAF) sensor, manifold absolute pressure sensor, or as a separate component. The signal from the sensor is used to adjust the ignition system dwell period (on a spark-ignition engine) and to measure the density of the intake air. This is important when used with a forced induction system, as the temperature of the air can increase after it has increased in pressure. The signal can also be used to calculate the desired output from the alternator when a smart charging system is used. The system can calculate the approximate temperature of the battery from this data.