Note: not all versions are equipped with an IAT sensor. For these versions the intake air temperature (downstream of the turbocharger) is calculated by the IAT sensor integrated in the MAF sensor.
Function
The IAT sensor is designed as an NTC thermistor and is located in the intake tract, downstream of the turbocharger. It detects the charge air temperature in order to compensate for the temperature influence on the density of the charge air.
The IAT signal influences the following functions:
โข Injected fuel quantity,
โข Injection timing,
โข EGR system.
Effects of faults
In the case of a fault, the PCM operates using a substitute value. This substitute value is derived from the ECT and fuel temperature.
Diagnosis
The PCM constantly checks whether the IAT sensor values are within the limits.
If the maximum limits are exceeded for a determined time, this is interpreted by the PCM as an open control loop or a short to positive.
If the minimum limits are not reached for a determined time, this is interpreted by the PCM as a short to ground. The rise/fall check permits the system to detect intermittent faults (for instance a loose connector contact).
In vehicles with a diesel particulate filter system (Emission Standard IV) a further check, the plausibility check, has been implemented.
For the plausibility check, the signals of the ECT sensor, the fuel temperature sensor, the IAT sensor in the MAF sensor and the separate IAT sensor are compared with one another once the engine has cooled down. In this condition, the temperature values are approximately the same.
If the check reveals that the IAT sensor values deviate from the other values by more than a specified limit, the IAT sensor is recognized as implausible and a DTC is stored.