Local CAN bus
The CAN bus (Controller Area Network) is a serial bus system, in which all connected stations are equally entitled, i.e. each control unit can both send as well as receive. In other words, the connected control units can "communicate" and exchange information via the lines.
Due to the linear structure of the network, the bus system is fully available for all other stations in the event of one station failing. The connection consists of two data lines (LOCAN_L and LOCAN_H).
The local CAN bus exists independently of the familiar CAN bus. The local CAN bus serves only engine functions. The data exchange across the Local CAN bus takes place between the following control units, depending on the engine variant:
DME control unit
Valvetronic control unit
HDEV control unit
The connected control units must all have the same CAN status. The CAN status can be checked via the diagnosis interface. The CAN status (bus index) is specified on the identification of the relevant control unit connected to the CAN bus
I'm guessing one of the three Control Units above failed to boot up properly.
My BMW ACS7