Steering Column: Description and Operation
32 02 03 (050)
Fully electric steering-column adjustment E60/E61/E63/E64
Introduction
The fully electric steering-column adjustment allows the driver to set the steering wheel to the best possible position. This is done with a switch on the left-hand side of the steering column. The angle and the reach of the steering column are electrically adjusted.
The steering column adjustment is actuated by the center console switch cluster (SZM).
One motor drives the tilt and reach adjustment. The second motor switches adjustment gears to select the adjustment direction.
[system overview ...]
The steering column adjustment is a constituent component of option 459 "Electric seat adjustment". Options 456 "Comfort seats, front" and 481 "Sports seats" automatically include option 459 "Electric seat adjustment".
Vehicles with electric steering-column adjustment have a steering-column memory (in conjunction with seat memory and mirror memory).
New from 09/05:
- The steering column switch cluster (SZL) is directly connected to the PT-CAN.
- The body gateway module (KGM) forms the gateway between the PT-CAN and the K-CAN.
Brief description of components
The steering-column adjustment consists of the following components:
- Switch for steering-column adjustment
This switch enables the driver to adjust the tilt and reach setting of the steering column. The switch for steering-column adjustment is on the left-hand side of the steering column.
- Steering-column adjustment drive unit
Two motors are built into the drive unit. 1 motor drives the tilt and reach adjustment of the steering column. The second motor changes the direction of adjustment via the adjustment gears.
The adjustment movement and position recognition for both tilt and reach adjustment are recorded in the drive unit for the steering-column memory. There are 2 Hall sensors and 2 magnetic rings (16-pin) integrated in the drive unit.
- Steering column switch cluster
The switch for steering-column adjustment sends its signal to the steering column switch cluster (SZL). The steering column switch cluster forwards this signal to the center console switch cluster (SZM).
>up to 09/05
Signal path: Switch for steering-column adjustment -> Steering column switch cluster (SZL) -> byteflight -> Safety and gateway module (SGM) -> K-CAN -> Center console switch cluster (SZM).
>from 09/05
Signal path: Switch for steering-column adjustment -> Steering column switch cluster (SZL) -> Body gateway module (KGM) -> K-CAN -> Center console switch cluster (SZM).
- Center console switch cluster
The center console switch cluster (SZM) actuates the steering-column adjustment. The center console switch cluster also stores the positions for the steering-column memory.
- Door contact in the driver's door
The center console switch cluster needs the signal from the door contact. The signal for easy entry and exit is used in conjunction with the terminal status.
>up to 09/05
Signal path: Driver's door contact switch -> Driver's door module (TMFA) -> byteflight -> Safety and gateway module (SGM) -> K-CAN -> Center console switch cluster (SZM).
> from 09/05
Signal path: Driver's door contact switch-> Body gateway module (KGM) -> K-CAN -> Center console switch cluster (SZM).
System functions
The fully electric steering-column adjustment comprises the following functions:
- Manual steering-column adjustment
- Steering-column memory
- Overheating protection for steering-column adjustment motors
Manual steering-column adjustment
The driver is able to adjust the steering column with a switch. When the switch is operated, the signal is transmitted cyclically from terminal 30 (cycle time: 100 milliseconds). The steering-column adjustment is actuated for as long as the signal is being received.
Once the switch is no longer actuated, the message "Stop" is transmitted 3 times.
The steering-column adjustment is stopped when this signal is received, or if the cyclic message is not received twice.
To enable a failure of the steering column switch cluster to be detected, a further a cyclic message is transmitted when the data bus is active (cycle time: 1 second).
When changing the direction of adjustment, the center console switch cluster first actuates the switching motor.
The actuation of this motor is time-dependent. The adjustment motor is not actuated until the direction of adjustment is correctly set. The total adjustment movement is no more than 36 millimeters for tilt adjustment and 40 millimeters for reach adjustment.
Steering-column memory
The position of the steering column in each direction of adjustment is recorded by a Hall sensor. This position is stored in the center console switch cluster (SZM). This allows the Key Memory to call up the position of the steering column for up to 4 vehicle keys.
The tilt adjustment moves to the uppermost position to make it easier to get in and out of the vehicle.
For the easy-access facility, the steering-column adjustment is automatically actuated under the following conditions:
- Terminal R OFF
- Terminal R ON and driver's door opened (via door contact)
- Terminal 15 OFF with driver's door open (via door contact)
The steering-column memory is activated under the following conditions:
- One of the two memory buttons for the seat-mirror memory and the steering-column memory on the seat is pressed (from terminal R OFF).
- Another remote control is used (personalization). Condition: The selection "Last seat position after unlocking" is activated in the "Settings" menu in the Central Information Display (CID) (from 09/03).
In both cases, the steering-column memory will not move the steering column to the stored position until terminal 15 is switched ON.
Overheating protection for steering-column adjustment motors
To protect the motors against overheating, a temperature model is stored in the center console switch cluster.
The temperature model makes allowance for the warming up and cooling down of the motors.
It is possible to move the steering column in either direction through the range of movement at least 6 times before overheating protection is activated.
Notes for service staff
Service staff should note the following points:
- General information:
- Diagnosis: ---
- Encoding/programming: ---
Subject to change.