M-Bus Topology
The M-bus consists of a three wire ribbon. On E38 vehicles because of the large number of stepper motors used, the M-bus is divided into two separate circuits. All other vehicles use a single M-bus cable. The M-bus wire ribbon is not routed with the rest of the vehicle harness but is a separate harness attached to the IHK housing.
Always refer to the ETM to determine the exact wiring configuration for a specific model.