The M67 features two control unit (referred to as master and slave) that are interconnected by means of a "private" CAN-bus.
Similar to the DDE 4.0, the control units are equipped with module connectors. Although the hardware of the control units is identical different data records have been programmed so the engine operation is not possible if the connectors are interchanged.
The two control units also feature 120 Ohm terminal resistors for the private CAN bus.
Fault codes 0600, 0601 "CAN bus private" are stored if a defect is detected on the private CAN bus. As a result, the engine is still conditionally operable on 4 cylinders, however, it will no longer start after being turned off.