Re: BMW X5 3.0 TD - Excess smoke, code 0501 EGR negative control deviation # Archived Message
Posted by Dave Harney on September 30, 2009, 3:23 pm, in reply to "Re: BMW X5 3.0 TD - Excess smoke, code 0501 EGR negative control deviation #"
Mass air flow sensor DDE 6.0 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: •Exhaust gas recirculation •Calculating limitation volume Function 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. Troubleshooting Faults in the component 'mass air flow sensor' result in one or more fault reactions: •Exhaust gas recirculation is deactivated •Deactivation of turbo pressure control •Volume limitation •Output of a substitute value dependent on engine speed
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