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

MODEL 204.0/2 with CODE (275) Memory package (driver seat, steering column, mirrors) as of model year 2009/YoM 08

MODEL 204.3 with CODE (275) Memory package (driver seat, steering column, mirrors)

MODEL 204.9 with CODE (275) Memory package (driver seat, steering column, mirrors)

Fig 1: Electrically Adjustable Steering Column (ESC) Block Diagram

Courtesy of MERCEDES-BENZ USA

Function requirements, general

Steering column normalized

Electrically adjustable steering column (ESC), general

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

The easy entry/exit function makes it possible for the driver to get in and out of the vehicle easily. In the process the steering column is moved upwards before getting in or out. The steering column is adjusted and the current position of the steering column is stored by the driver seat control unit by actuating the steering column up/down adjustment motor.

Normalization of the steering column is important for the limitation of the adjustment range.

For normalization of the steering column the respective limit stops of the steering column adjustment are approached and the counter reading of the Hall sensor signals is stored as the normalizing position.

The electrically adjustable steering column includes the following subfunctions:

Function sequence for adjust/store steering column
Function sequence for steering column adjustment easy entry and exit feature

Function sequence for adjust/store steering column

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

The store/adjust steering column function is comprised of the following subfunctions:

D Function sequence for adjust steering column

D Function sequence for save position of steering column

D Function sequence for call up saved steering column position

Function sequence for adjust steering column

Adjustment of the steering column is requested by pressing the steering column adjustment switch.

The status of the steering column adjustment switch is read in by the steering column tube module control unit and sent to the chassis CAN. The front SAM control unit routes this over the interior CAN to the driver seat control unit. The driver seat control unit actuates the steering column in/out adjustment motor or the steering column up/down adjustment motor to match the requirement.

Actuation continues for as long as the steering column adjustment switch is held down or until an end stop is reached.

Function sequence for save position of steering column

The current position of the steering column can be stored together with the position of the driver seat and the position of the outside mirrors.

The position of the steering column is defined by the Hall sensors integrated in the steering column adjustment motors.

The store function is requested by pressing one of the following memory switches in the left front seat adjustment switch group and the left front memory function switch (S22s6). The following switches are integrated in the left front seat adjustment switch group:

Left front memory 1 switch (S22s7)
Left front memory 2 switch (S22s8)
Left front memory 3 switch (S22s9)

The left front door control unit reads in the status of the switches in the seat adjustment switch group over the left door LIN and sends the corresponding request to the driver seat control unit over the interior CAN.

The driver seat control unit receives the request and stores the current position of the steering column adjustment motors and therefore the position of the steering column. Up to three different data records can be stored.

The instrument cluster emits an acknowledgment tone when the position is saved.

The current positions can be stored in different ways:

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

Function sequence for call up saved steering column position

Pressing a memory switch issues the request to move the driver seat, outside mirrors and steering column to a previously stored position.

The memory switch must be held down until the stored end position is reached.

Releasing the memory switch causes the adjustment process to be terminated immediately.

The left front door control unit reads in the status of the memory switch via the left door LIN and sends the corresponding request to the driver seat via the interior CAN.

The driver seat control unit actuates the steering column adjustment motors accordingly.

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

The easy entry and exit feature is activated through the instrument cluster
Drive position stored

Function sequence for steering column adjustment easy entry and exit feature

The easy entry/exit function makes it possible for the driver to get in and out of the vehicle easily. In the process the steering column is moved upwards before getting in or out.

The easy entry/exit function can be activated or deactivated in the instrument cluster via the "Settings" menu in the "Comfort" submenu. The corresponding selection is made using the multi function steering wheel button groups.

The signals of the multifunction steering wheel button groups are read in by the steering wheel electronics and sent over the steering LIN to the steering column tube module control unit. The steering column tube module control unit routes the signals over the chassis CAN to the instrument cluster.

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

The steering column adjustment easy entry and exit feature is comprised of the following subfunctions:

D Function sequence for move to easy entry/exit position

D Function sequence for move to drive position

D Function sequence for repeat limiter

Function sequence for crash-active easy entry and exit feature (as of 1.6.09)

Additional function requirements, approach easy entry/exit position

Intentionally leaving the vehicle by removing the transmitter key (A8/1) from the electronic ignition lock control unit
Driver door opened

Function sequence for move to easy entry/exit position

Before the steering column is moved to the exit position, the driver seat control unit stores the current position of the steering column (driving position) so that the steering column can be moved back to its initial position again after the adjustment process. The circuit 15 status is sent by the electronic ignition lock control unit to the interior CAN.

The status of the driver door, as defined by the status of the left front door rotary tumbler switch (A85s1), is sent to the interior CAN by the left front door control unit.

The driver seat control unit reads in all relevant information and actuates the steering column up/down adjustment motor accordingly.

Function sequence for move to drive position

After the driver has got into the vehicle, the steering column is moved back to the 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 with driver door closed
Change from circuit 15C to circuit 15R with driver door closed
Change from circuit 15R to circuit 15 ON with driver door closed

The circuit 15 status is sent by the electronic ignition lock control unit to the interior CAN.

The status of the driver door is placed on the interior CAN by the left front door control unit.

The driver seat control unit reads in all relevant information and actuates the steering column up/down adjustment motor accordingly.

Function sequence for repeat limiter

The repeated insertion and removal of the transmitter key in and out of the electronic ignition lock control unit causes a switchover between the "move to entry/exit position" function and the "move to drive position" function. In order to prevent overload of the steering column adjustment motor high and low, the number of requests is limited to five adjustment cycles

The number of adjustment cycles is reset as soon as the electronic ignition lock control unit sends the status of circuit 15R or when the left front door control unit (with left-hand drive vehicles) signals the "driver door open" or "driver door closed" status.

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 of Hall sensor integrated into steering column up/down adjustment motor

Function sequence for crash-active easy entry and exit feature (as of 1.6.09)

Following the occurrence of a crash event the driver seat and the steering column are automatically moved upwards to a defined position.

The crash signal is sent by the supplemental restraint system control unit over the chassis CAN to the front SAM control unit and forwarded from there over the interior CAN to the driver seat control unit.

The driver seat control unit then actuates the steering column adjustment up/down motor.

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