Steering Column: Description and Operation

Electric Steering Column Adjustment

Electrical steering column adjustment
The electrical steering column adjustment enables the driver to set the optimized position of the steering wheel.
There is a switch on the left of the steering column for operation. The inclination and length of the steering column are adjusted electrically. The control for the electrical steering column is located in the IHKA control unit.

Brief description of components
The following components are described for the electrical steering column adjustment:

Switch for steering column adjustment
The driver can use this switch to adjust the inclination and length of the steering column. The switch for the steering column adjustment is on the left of the steering column.

Steering column adjustment unit
The steering column adjustment unit is a composite component and contains a number of components. The integrated components are:
- Steering column adjustment motor
- Solenoid
- Hall sensor on the steering column adjustment motor
- Hall sensors for Soft-stop







Steering column adjustment motor
The steering column adjustment motor adjusts the angle and length of the steering column.

Solenoid
The solenoid changes the adjustment direction as regards length and angle.

Hall sensor on the steering column adjustment motor
The Hall sensor on the steering column adjustment motor passes on a signal to the IHKA control unit on adjustment of the steering column. The IHKA control unit then determines the position of the steering column.

Hall sensors for Soft-stop
The Hall sensors for the Soft-stop detect when the steering column is approaching the limit position.

Driver's door contact
The IHKA control unit requires the signal from the door contact. In conjunction with the terminal status, the signal for Easy Entry / Easy Exit is used.
Signal path: Door contact driver's door - Footwell module (FRM) - K-CAN - IHKA control unit
The following control units are involved in the electrical steering column adjustment:

IHKA: Control unit
The IHKA control unit activates the electrical steering column adjustment. The IHKA control unit is supplied with voltage via terminal 30 G (with 20 A fuse). The IHKA control unit is activated via the wake-up line (terminal 15).
The positions for the steering column memory are also stored in the IHKA control unit.







System functions
The following system functions are described for the electrical steering column adjustment:
- Steering column adjustment
- Steering column memory
- Overheating protection for the steering column adjustment motor

Steering column adjustment
The driver can use a switch to adjust the steering column.







The electrical steering column adjustment has a Soft-stop for the axial and vertical axis. When the end of the axle approaches the Hall sensors for the Soft-stops, activation of the steering column is stopped. If the Hall sensors for the Soft-stops were defective, the steering column adjustment motor would encounter blocking current on reaching the end position and would be switched off.

Steering column memory
The position of the steering column is picked up by the Hall sensor directly at the electric motor. The position is then sent to the IHKA control unit and stored in the IHKA control unit. For the key memory, this means that the position of the steering column can be called up for all ignition keys.
To support entry and exit, the inclination adjustment moves to the highest position.
For Easy Exit, the steering column adjustment is automatically activated under the following conditions:
- Terminal R OFF
- Terminal R On and driver's door is opened (via door contact)
- Terminal 15 Off with opened driver's door (via door contact)

The steering column memory is activated under the following conditions:
- One of the two memory buttons for the seat memory and the steering column memory on the seat is pressed (as of terminal R Off).
- Another identification sensor is used (personalization). Condition: in the Central Information Display (CID) the selection "Last seat position after unlocking" is activated in the "Settings" menu.

In both cases, the steering column memory only moves to the corresponding memory position after terminal 15 On.

Notes for Service department

Diagnosis instructions
After coding or programming the IHKA control unit, standardization of the steering column is to be run. After repair work on the electrical steering column adjustment, the service function "Standardization" is also to be run.

NOTE: Failure of the Hall sensor on the motor

In the event of failure of the Hall sensor, no identification of the position is possible for the steering column adjustment. In the same way, the system cannot move to any position stored in the memory. The Soft-stop is switched off. The time for activation of the overload protection is shortened. This protects the steering column adjustment motor against overheating.


NOTE: Failure of the Hall sensors for the Soft-stops

In the event of failure of the Hall sensors for the Soft-stops, the time for activation of the overload protection is shortened. This protects the steering column adjustment motor against overheating.

NOTE: System state due to cold

Blocking of the steering column adjustment due to cold is regarded as a mechanical stop. This might mean that the adjusting path in one adjustment direction is restricted.

Notes on coding / programming

IMPORTANT: IHKA control unit

After coding or programming the IHKA control unit, standardization of the steering column is to be run.
No liability can be accepted for printing or other errors. Subject to changes of a technical nature