The fully electric steering column adjustment enables the driver to set the steering wheel to a convenient position. Here, the steering column can be moved by electric motors in two levels. The driver can use the steering-column adjustment switch to set length and tilt of the steering column manually. Various positions of the steering column can be stored in the seat memory and called up; the steering column then sets itself to the specified position. In the case of automatic convenience entry (entry and exit), the steering column moves to the most forward and highest position. After deactivation of automatic convenience entry, the steering column returns to the original position.
Control units
The fully electric steering column adjustment function is integrated in the Chassis Integration Module (CIM). The CIM control unit controls the motor gearing units for the longitudinal and tilt adjustment of the steering column.
The memory positions are stored and administered by the driver seat module (SM_FA). If the memory is invoked, the coordinates for the steering column are sent by the SM_FA control unit to the CIM control unit via the K-CAN SYSTEM.
Electric motor for longitudinal adjustment of the steering column
The electric motor for longitudinal adjustment of the steering column adjusts the steering column longitudinally by means of a gearing unit.
Electric motor for tilt adjustment of the steering column
The electric motor for tilt adjustment of the steering column adjusts the inclination of the steering column by means of a gearing unit.
Steering-column adjustment switch
The steering-column switch is used to set the steering column manually. The steering-column adjustment switch transmits the information for the longitudinal and tilt adjustment of the steering column via the steering column switch centre (SZL), the BYTEFLIGHT, the Safety and Information Module (SIM) and the K-CAN SYSTEM to the CIM control unit.
Driver's door contact via the K-CAN SYSTEM
The driver's door contact sends its signal via the Car Access System (CAS) and the K-CAN SYSTEM to the CIM control unit. The signal is required for the automatic convenience entry.
Manual steering column adjustment
Manual adjustment is performed by the driver by operating the steering-column adjustment switch. The signal is received by the CIM control unit via the K-CAN System. The signal ”operation steering column adjustment” is transmitted in cycles when the adjusting switch is operated. When the switch is no longer being operated, the signal ”not operated” comes once. The CIM control unit activates the relevant servomotor while the signal is being received and stops with the signal ”not operated”. If the cyclic adjustment signal fails on two occasions, the steering column adjustment is also stopped.
Automatic steering column adjustment as memory call-up
The position of the steering column is registered by a Hall sensor on each servomotor in that the relative path from each starting position is measured and stored. These coordinates can be saved via the K-CAN SYSTEM in the driver's seat module (SM_FA). If the memory is invoked, the stored coordinates are sent to the CIM control unit. The CIM control unit activates the servomotor until the specified position of the steering column is reached.
Automatic steering column adjustment as automatic convenience entry
When the automatic convenience entry is activated, the following sequence is started:
1. The tilt adjustment moves to the top position. 2. The longitudinal adjustment moves the most forward position (direction of travel).
The control of the automatic convenience entry is dependent on the following signals:
- Terminal_R, comes from the Car Access System (CAS) - Terminal_15, comes from the Car Access System (CAS) - signal driver's door contact
These signals are received by the CIM control unit via the K-CAN System. The automatic convenience entry is activated when:
Terminal_15 and Terminal_R are switched off Terminal_15 is switched off with the driver's door open, the driver's door is opened after Terminal_15 is switched off (but Terminal_R = on).
The automatic convenience entry is deactivated when Terminal_15 is activated. The steering column moves to its normal position.
Important note!
In the case of a voltage drop below 7.5 V, the stored position data of the steering column in the CIM control unit becomes invalid. The fault 5D38 'Position data, steering column' is stored in the fault code memory. The stored steering column position can no longer be called up from the seat memory. When the system voltage reaches the normal value again, the CIM control unit regenerates itself. The position data are valid again. The memory position of the steering column, however, must be stored anew in the seat memory. Delete the fault code memory.