Active multicontour seat function - GF91.25-P-0004FQ

MODEL 218 with CODE 432 (Active multicontour seat) 

For vehicles with code (494) USA version only the driver seat is an active multicontour seat.

Function requirements, general 

• Circuit 15 or circuit 15R ON
• No overvoltage or undervoltage

The electronic ignition lock control unit transmits the status of circuit 15 via the interior CAN to the active multicontour seat control units.

Active multicontour seat, general 

The active multicontour seat combines the advantages of a comfortable multicontour seat with those of a sport seat. The contour and surface hardness of the backrest and the seat cushion of the driver and front passenger seat can be changed individually. This is done by air cushions that can be inflated independently of each other.

The air cushions are installed in the following areas:

• Lower lumbar area
• Upper lumbar area
• In the side bolsters of the backrest (lateral support)
• Front area of seat cushion (seat cushion length)

The lateral support in the driver and front passenger seat is made possible by a basic pressure in the lateral support air cushions. The dynamic function boosts the lateral support when cornering by automatically increasing the pressure in whichever lateral support air cushion is on the outside of the curve.

To prevent any tension in the back during long journeys, the multicontour seats are equipped with a massage function (pulse mode). As long as this is active, the contour of the seven-row massage insert is sequentially altered by building up, maintaining and relieving the pressure. The pulsation takes place in pressure jumps in the upward or downward direction. The dwell time can be set with the diagnostic tester.

The air supply, required for inflating the air cushion, is provided by the active multicontour seat pneumatic pump. The respective active multicontour seat control unit transmits the request to switch on via the interior CAN to the active multicontour seat pneumatic pump. The status of the active multicontour seat pneumatic pump is read in by the respective active multicontour seat control unit via the interior CAN.

PRE-SAFE:

In critical situations, the seat contour of the driver or front passenger seat is automatically changed to achieve a favorable seat position and securing of the occupant. Detailed information about this can be found in the following separate "PRE-SAFE function" function description:

The active multicontour seat function includes the following subfunctions:

• Function sequence for manual adjustment of the air cushions 
• Function sequence for the storage and retrieval of air cushion settings (with code (275) Electrically adjustable front seats, memory package) 
• Function sequence for dynamic function 
• Function sequence for massage function 

Function sequence for manual adjustment of the air cushions 

Individual settings can be made at the driver and front passenger seat via the active multicontour seat button groups.

The following seat areas can be adjusted:

• Lower lumbar area
• Upper lumbar area
• Side bolsters of the backrest (lateral support)
• Front area of seat cushion (seat cushion length)

The respective active multicontour seat control unit reads in the control signals of the active multicontour seat button group directly and evaluates them. The inflation and deflation of the individual air cushions is controlled by the respective active multicontour seat control unit by actuating the integrated piezo valves. The pressure values are recorded by integrated pressure sensors and stored by the respective active multicontour seat control unit.

Short-term and long-term control

The short-term control compensates for overpressure deviations in the air cushions. It activates following every adjustment and only remains active for a short, parameterizable period of time. The short-term control is used among others to compensate for sitting down or leaning back immediately and in a comfort-oriented fashion. After the short-term control, the long-term control becomes active. Here, the pressure supply is regulated such that the specified pressure is always achieved. Control is carried out by the respective active multicontour seat control unit.

The manual adjustment is aborted under the following conditions

• Overvoltage or undervoltage
• Inflation or deflation timeout
• Leak in one or more air cushions
• Active multicontour seat button group has short circuit to ground or is jammed

Manual adjustment of the air cushions is inhibited if the following faults occur:

• Inflation or deflation timeout
• Active multicontour seat button group has short circuit to ground or is jammed

Function sequence for the storage and retrieval of air cushion settings (with code (275) Electrically adjustable front seats, memory package) 

The set pressures in the air cushions of the driver and front passenger seat and the settings of the dynamic function can be saved and subsequently retrieved.

There are two options for saving the settings made:

• Press the respective front memory function switch and hold, then press the respective front memory 1 switch, front memory 2 switch or front memory 3 switch.
• Press the respective front memory function switch for t > 100 ms and release, then press relevant memory switch 1, 2 or 3 within t ≥ 0.2 to 3 s.

The respective front door control unit reads in the command requests of the individual switches at the relevant front seat adjustment switch group via the front door LIN and transmits this via the interior CAN to the driver seat control unit or the front passenger seat control unit. The driver seat control unit or front passenger seat control unit transmits the "Store memory position" request via the interior CAN to the respective active multicontour seat control unit. The respective active multicontour seat control unit stores the air cushion setting based on the signals from the integrated pressure sensors.

When operating the memory function from the driver side, the seat setting, the setting for the steering column and the settings for both outside mirrors are stored.

Stored values can be overwritten at any time. The save process is canceled in the event of an active manual adjustment.

Stored settings can be retrieved by pressing a memory switch. The respective front door control unit reads in the status of the memory switch via the front door LIN and transmits this via the interior CAN to the driver seat control unit or front passenger seat control unit. The driver seat control unit or front passenger seat control unit transmits the "Adopt memory position" request via interior CAN to the respective active multicontour seat control unit.

Additional function requirements for the dynamic function 

• Vehicle speed v > 10 km/h
• Steering wheel angle change > 9°
• Seat occupancy detected or seat belt buckle inserted (front passenger seat)

The instrument cluster transmits the vehicle speed via the interior CAN to the active multicontour seat control units.

The steering wheel angle is recorded by the steering wheel sensor. The steering column tube module control unit reads in the signals of the steering angle sensor directly and transmits them via the chassis CAN (up to 28.2.13) or chassis CAN 1 (as of 1.3.13), the front SAM control unit and the interior CAN to the active multicontour seat control units.

Detailed information on seat occupancy recognition and the seat belt buckle status is included in the separate function description for the "Supplemental Restraint System Function".

Function sequence for dynamic function 

The dynamic function boosts the lateral support when cornering by increasing the pressure in whichever lateral support air cushion is on the outside of the curve. The intensity of the lateral support can be adjusted in two stages.

The dynamic function is selected by pressing the Dynamics button:

• Pressed once: stage 2 (sport, both LEDs on)
• Pressed twice: stage 1 (standard, one LED on)
• Pressed three times: dynamic function off (both LEDs off)

The selected stage is indicated by one or both LEDs in the corresponding dynamics button lighting up. The respective active multicontour seat control unit reads in the status of the dynamic button directly and actuates the LED in the dynamic button in accordance with the selected stage.

Depending on the vehicle speed, the steering wheel angle change and the vehicle's motion (lateral acceleration), the respective active multicontour seat control unit briefly increases the air pressure in the outside lateral support air cushion.

The Electronic Stability Program control unit (without code (233) DISTRONIC PLUS, except model 218.374/974) or the Premium Electronic Stability Program control unit (with code (233) DISTRONIC PLUS, and model 218.374/974) transmits information about the vehicle's motion via the chassis CAN (up to 28.2.13) or chassis CAN 1 (as of 1.3.13), the front SAM control unit and the interior CAN to the respective active multicontour seat control unit.

The dynamic function is interrupted under the following conditions:

• Overvoltage or undervoltage
• Inflation or deflation timeout
• Leak in one or both lateral support air cushions
• On-board electrical system emergency running mode
• No information about the vehicle's self-movement
• Memory adjustment (with code (275) Electrically adjustable front seat memory package)
• Active multicontour seat button group has short circuit to ground or is jammed

If the following faults occur, the dynamic function is blocked but the LEDs in the dynamics button remain switched on:

• Inflation or deflation timeout
• Active multicontour seat button group has short circuit to ground or is jammed

Function sequence for massage function 

The massage function is a convenience function and lets the driver or front passenger relax, in particular during longer trips. Intensity can be adjusted in two stages. The respective active multicontour seat control unit moves a slide valve in a cylinder with seven air outlets. By moving the slide valve, the air outlets to the rows of air cushions for the massage insert are opened or closed. The respective active multicontour seat control unit can move the slide valve to a total of 23 slider positions and hold it there. The individual positions are compared to a reference position (limit switch). The front seat massage function actuator motor is actuated directly by the respective active multicontour seat control unit. The status of the limit switch is read in directly by the respective active multicontour seat control unit.

The massage function is selected by pressing the massage function button:

• Pressed once: Massage program 1 (undulating, both LEDs on)
• Pressed twice: Massage program 2 (rolling, one LED on)
• Pressed three times: Massage function off (both LEDs off)

The selected massage program is indicated by one or both LEDs in the corresponding massage function button lighting up. The respective active multicontour seat control unit reads in the status of the massage function button directly and actuates the LED in the massage function button in accordance with the selected stage.

Massage program 1 (undulating):

After pressing the massage function button, the respective active multicontour seat control unit opens the air supply via the main valve to the front seat massage function actuator motor. Starting with the lower massage air cushion row (row 1), the contour changes sequentially through inflation, maintenance of the pressure and deflation. After a defined waiting time the cycle for the next massage air cushion row (row 2) is started on the same pattern. When the waiting time for inflating the last massage air cushion row (row 7) has elapsed, the cycle continues with the bottom massage air cushion row (row 1). The front seat massage function actuator motor has a total of 23 slide positions which it can moved to during a massage cycle. The pressure difference between the deflated and the inflated massage cushion is approx. p = 100 mbar. A wave motion is created by alternately deflating and inflating the rows of massage air cushions. After approx. t = 8 min, massage program 1 ends automatically.

Massage program 2 (rolling):

Starting with the lower massage air cushion row (row 1), the contour changes sequentially through inflation, maintenance of the pressure and deflation. After a defined waiting time the cycle for the next massage air cushion row (row 2) is started on the same pattern. When the waiting time for inflating the last massage air cushion row (row 7) has elapsed, the cycle continues with the next massage air cushion row (row 6). The remaining massage air cushion rows are then activated successively in the reverse order. After approx. t = 12 min, massage program 2 ends automatically.

In both programs the massage function can be performed with two characteristics (weak or strong). This results in four massage programs that can be assigned via variant coding.

The active massage program is interrupted under the following conditions:

• Manual lumbar support adjustment
• Manual adjustment of lateral support
• Memory adjustment (with code (275) Electrically adjustable front seat memory package)

The massage function is interrupted under the following conditions:

• Overvoltage or undervoltage
• Reference position in the seat massage function actuator motor not OK
• Target position in seat massage function actuator motor not reached
• Overloading of the active multicontour seat pneumatic pump
• Adjustment request by PRE-SAFE
• Active multicontour seat button group has short circuit to ground or is jammed

The massage function is blocked if the following faults occur:

• Reference position in the seat massage function actuator motor not OK
• Active multicontour seat button group has short circuit to ground or is jammed

	Electrical function schematic for active multicontour seat		PE91.25-P-2052-97XAA
	Overview of system components, electric seats		GF91.29-P-9992FQ