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In Reply to: Prob you DK motor for one bank posted by Sean on January 17, 2000 at 14:41:54:
Sean is, as usual, correct except for one small nit:
The electronic throttle system comprises of two DK motors and a single EML controller. The two Motronics really don't have any active role in the movement of the throttles. You press the pedal, it transmits a voltage (or AC frequency in EML-III) to the EML unit, which then calculates a throttle plate position voltage. The DK motor moves the throttle plate thru a reduction gearbox (direct drive in EML-III). The throttle butterfly position is sensed using a feedback potentiometer, again sending a voltage back to the EML confirming throttle position.
The primarily failure modes are 1) feedback pots wearing out and 2) excessive wear and lash in the reduction gearbox. Enough of either of these (among other factors), and the EML computer determines there's a fault and takes the DK offline. It's all done since EML is a critical safety sytstem and integrity has to be high.
BMW moved from Bosch (EML-II) to Siemens (EML-III) in 1995 to improve the reliability and simplicity of the setup. There have also been several firmware updates over the years.
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