CTM: Convertible-top module

The Convertible Top Module (CTM) is the central control unit for all functions of the retractable hardtop. The CTM is fitted on the right on the partition. The CTM controls the retractable hardtop, the rear module and the Soft Close Automatic system. The CTM controls the drive for hardtop locking. The CTM also controls the hydraulic pump and the 8 hydraulic cylinders via the 5 valves in the hydraulic unit. The CTM is connected by the K-CAN to other control units. In this way, e.g., information on the ambient temperature, driving speed and status of the luggage compartment lid is received via K-CAN. On opening and/or closing the hardtop, the CTM sends a signal to the Car Access System (CAS). The CAS serves as the master controller for the electric power windows. The CAS sends CAN signals to activate the footwell module (FRM) as well as the junction box electronics (JBE). The signal serves as a command to lower the front and rear side windows. Under specific conditions the customer will receive messages in the form of Check Control reports in the instrument cluster.

Fig 1: Identifying Convertible Top Module Components

Courtesy of BMW OF NORTH AMERICA, INC.

Depending upon whether the roof is open or closed: The CTM transmits a signal to the Diversity aerial requesting aerial changeover.