The intake air temperature sensor is integrated in the mass air flow sensor on vehicles with engine management system MS45. A precision ballast resistor (NTC resistor) is used to convert the temperature into a measurement value which can be evaluated electrically by the DME control unit.
The intake air temperature sensor is not required for correction of the fuel injection period, as the intake-air temperature is automatically taken into account in the air mass metering. The intake air temperature sensor is set at the start procedure in conjunction with the engine coolant temperature sensor. The resistance values of both sensors supply exact information for calculating the fuel injection period. In this way hot start problems in particular are avoided.
The air column in the mass air flow sensor can oscillate during a start procedure. For this reason, the value output by the mass air flow sensor cannot be used as a correct value for fuel injection period. The temperature sensors are therefore used as a measured variable up to a freely programmable engine speed threshold.