Air Temperature Sensor ( Ambient / Intake ): Description and Operation

Intake Air Temperature Sensor

Sensor Stuck
This monitor checks that the IAT sensor is not stuck at a particular value. If the airflow into the engine is over a threshold for greater than a calibratable time, then the IAT sensor reading is stored. The next time the airflow into the engine drops below a second threshold and the engine is idling, then a second timer is incremented. Once this timer reaches a pre-determined value, then the IAT sensor reading is stored again. The high flow temperature is subtracted from the low flow temperature and if the difference is greater than a threshold, then a normal judgement will be made. If the result is less than the threshold then a failure will be detected.

Range or Performance Failure
The monitor checks that the IAT sensor is reading a correct value when compared to other sensors on the vehicle.

If the engine has been off for greater than a calibrated time period, then the IAT sensor reading is compared to the average of the sum of the ECT sensor and AAT sensor. The IAT sensor must be within a calibrated threshold of this reading for a normal judgement to be made. If it is outside this threshold then a failure is flagged.

Range/Performance Flow chart