Electrically adjustable steering column (ESC), function - GF46.15-P-0003FQ

MODEL 218 with CODE 275 (Electrically adjustable front seats memory package)

Fig 1: Electrically Adjustable Steering Column Block Diagram

Courtesy of MERCEDES-BENZ USA

Function requirements, general

No overvoltage or undervoltage

Electrically adjustable steering column, general

The electrically adjustable steering column function allows the steering column to be adjusted as required and increases comfort when getting into and out of the vehicle.

The electrically adjustable steering column function includes the following subfunctions:

Function sequence for normalization
Function sequence for adjusting/saving steering column
Function sequence for steering column adjustment easy entry and exit feature

Function sequence for normalization

Normalization is the basis for assignment of the current position to the steering column position detected by the driver seat control unit. Normalization must be performed during initial startup or in a denormalized condition. For this purpose, the front and top mechanical limit stop of the steering column must be approached.

During the initial startup, the normalization is performed with the diagnostic tester. After denormalization, the normalization procedure can be performed using the adjustment function. To do this, the steering column adjustment switch must be pressed and held for t = 250 ms after each mechanical end stop has been reached. The steering column tube module control unit reads in the switch position of the steering column adjustment switch directly and sends this position via the chassis CAN (up to 28.2.13) or chassis CAN 1 (as of 1.3.13), front SAM control unit and interior CAN to the driver seat control unit. The driver seat control unit directly actuates the corresponding steering column adjustment motor, reads in the signals directly from the respective steering column Hall sensor and evaluates these signals. Upon successful normalization, the driver seat control unit switches off the corresponding steering column adjustment motor.

Additional function requirements for adjust/store steering column

No Hall sensor fault present

Function sequence for adjusting/saving steering column

The adjust/store steering column function allows the steering column to be adjusted to various positions and these positions to be stored.

The adjust/store steering column function includes the following subfunctions:

Adjust steering column function sequence
Function sequence for save position of steering column
Function sequence for call up saved steering column position

Adjust steering column function sequence

The steering column is adjusted by operating the steering column adjustment switch. The steering column tube module control unit reads in the switch position of the steering column adjustment switch directly and sends this position via the chassis CAN (up to 28.2.13) or chassis CAN 1 (as of 1.3.13), front SAM control unit and interior CAN to the driver seat control unit. The driver seat control unit directly actuates the corresponding steering column adjustment motor, reads in the signals directly from the respective steering column Hall sensor and evaluates these signals. Actuation continues for as long as the steering column adjustment switch is pressed or until an end stop is reached.

Function sequence for save position of steering column

The current position of the steering column can be saved together with the position of the driver seat and the outside mirror. It is stored using the left front seat adjustment switch group.

The following possibilities exist to do this:

Press and hold down the memory function switch and then press the corresponding memory switch.
Press the memory function switch for t > 100 ms and then release it, and then press the corresponding memory switch within t ≥ 0.2 s to t ≤3 s.

The left front door control unit reads in the status of the corresponding switches in the left front seat adjustment switch group via the left front door LIN and sends the "Store memory position" request via the interior CAN to the driver seat control unit. The driver seat control unit uses the signals from the steering column Hall sensors to save the current position of the steering column. Up to three different data records can be stored.

When the position of the steering column has been successfully stored, an acknowledgment tone is output by the instrument cluster. The request for this is sent by the drivers eat control unit over the interior CAN to the instrument cluster.

Function sequence for call up saved steering column position

To move to a stored position, the corresponding memory switch must be pressed and held down until the steering column has reached the stored position. Releasing the switch causes the adjustment procedure to be aborted immediately. The left front door control unit reads in the status of the respective memory switch via the left front door LIN and sends the "Adopt memory position" request via the interior CAN to the driver seat control unit. The driver seat control unit then directly actuates the steering column adjustment motors.

Additional function requirements for steering column adjustment easy entry and exit feature

Easy entry/exit activated in the instrument cluster
Drive position stored

The instrument cluster sends the status of the easy entry/exit function to the driver seat control unit over the interior CAN.

Function sequence for steering column adjustment easy entry and exit feature

The easy entry/exit function allows the driver to enter or exit the vehicle in a more comfortable way. The steering column is moved upwards before entering or exiting the vehicle. The easy entry/exit function can be switched on and off via the "Setup" menu in the instrument cluster.

The steering column adjustment easy entry/exit function includes the following subfunctions:

Function sequence for move to easy entry/exit position
Function sequence for move to drive position
Function sequence for repeat limiter
Function sequence for crash-active easy exit feature

Function sequence for move to easy entry/exit position

The function is actuated when circuit 15C is switched off or the driver door is opened with circuit 15C or circuit 15R ON. The electronic ignition lock control unit sends the circuit 15 status over the interior CAN to the driver seat control unit. The left front door control unit reads in the status of the left front door rotary tumbler switch in the left front door lock directly and sends this status via the interior CAN to the driver seat control unit. To define the position of the steering column, the signals from the steering column up/down Hall sensor are read in directly and evaluated by the driver seat control unit. The driver seat control unit reads in all relevant information, stores the current position of the steering column (driving position) and actuates the steering column up/down adjustment motor accordingly.

Function sequence for move to drive position

The driver seat control unit actuates the steering column up/down adjustment motor under the following conditions in order to return the steering column to the drive position:

Closing driver door with circuit 15 On
Change from circuit 30 to circuit 15C On with driver door closed
Change from circuit 15C On to circuit 15R On with driver door closed
Change from circuit 15R On to circuit 15 On with driver door closed

The electronic ignition lock control unit sends the circuit 15 status over the interior CAN to the driver seat control unit. The left front door control unit reads in the status of the left front door rotary tumbler switch in the left front door lock directly and sends this status via the interior CAN to the driver seat control unit. The driver seat control unit reads in all relevant information and actuates the steering column up/down adjustment motor according to the stored data.

The functions approach entry/exit position or approach driving position are aborted under the following conditions:

Undervoltage or overvoltage
Manual adjustment request over the steering column adjustment switch
Memory adjustment request
Reversal of circuit 15 transition or driver door status change
Defect in one of steering column Hall sensors

Function sequence for repeat limiter

In order to prevent the steering column up/down adjustment motor from overloading in the case of repeated switching on/off of the "Move to entry/exit position" and "Move to driving position" functions, the number of adjustment cycles is limited to five only. This is reset as soon as the electronic ignition lock control unit sends the status of circuit 15R or if the left front door control unit sends the "Driver door open" or "Driver door closed" status.

Function sequence for crash-active easy exit feature

To make it easier for the driver to exit the vehicle or for first aiders to remove the driver from the vehicle after an accident, following a crash event the steering column is automatically moved upward to a predefined position if the following occurs:

Driver door opened
Change of status from circuit 15C ON to circuit 15C OFF

The electronic ignition lock control unit sends the circuit 15 status over the interior CAN to the driver seat control unit. The left front door control unit reads in the status of the left front door rotary tumbler switch in the left front door lock directly and sends this status via the interior CAN to the driver seat control unit. The Supplemental Restraint System control unit sends the crash signal via the chassis CAN (up to 28.2.13) or chassis CAN 1 (as of 1.3.13), front SAM control unit and interior CAN to the driver seat control unit.

To move the steering column upward, the driver seat control unit directly actuates the steering column up/down adjustment motor.

	Electrical function schematic for steering column adjustment		PE46.15-P-2050-97XAA
	Electrical function schematic for steering column easy entry/exit adjustment		PE46.15-P-2051-97XAA
	Overview of system components, electric seats		GF91.29-P-9992FQ