The mass air flow sensor measures the mass of fresh air drawn in by the engine.
The air mass serves as a measurement variable in the DDE control unit for the following functions:
The DDE control unit supplies the mass air flow sensor with voltage. The earth contact is across the cable M_HFM. The mass air flow sensor returns the air mass value via the signal T_HFM to the DDE control unit.
The signal is a square-wave signal with an amplitude of 5 V and frequency between 1.2 and 14 kHz. This frequency corresponds to a period duration of 0.8 - 0.07 ms.
The DDE control unit uses the frequency of this signal to calculate the air mass value with the unit mg/stroke.
Faults in the component 'mass air flow sensor' result in one or more fault reactions: