BMW Cars 1999-06

Distributorless Ignition System


Disconnecting the negative battery cable on some vehicles may interfere with the functions of the on board computer systems and may require the computer to undergo a relearning process.

All ignition and fuel injection functions are controlled by the Digital Motor Electronics (DME) control unit. Ignition timing is fully electronically controlled; there is no vacuum advance or manual adjustment. Ignition functions are calculated from internal maps and from the same sensors used for the fuel injection system. Vehicles with an automatic transmission, the control unit will retard ignition timing briefly when the transmission is about to shift up or down. For this reason, there is a data link between the DME control unit and the transmission control unit.

Variations of this ignition system are used on different engines. The M50B25 engine uses distributorless ignition with a coil pack mounted above each spark plug.