BMW 7 Series: Front Lumbar Support

Using lumbar support, the backrest can be individually adapted to the spinal column and thus ensures relaxed driving. Lumbar support is a standard feature in the multifunction seat.

The button for the lumbar support adjustment is located on the side of the front seat and is connected via the LIN bus to the seat module. The function of the lumbar support is integrated completely in the seat module. The lumbar support is adjustable from terminal 30B ON.

Fig. 102: Identifying Seat Adjustment Switches And Lumbar Support Switch

COMPONENTS DESCRIPTION CHART

1. Button for lumbar-support adjustment

4. Backrest inclination and head restraint adjustment
5. Longitudinal seat, seat-height and seat inclination adjustment

The seat module requests the button status for the lumbar support adjustment via the LIN bus an on a cyclical basis. Lumbar support is provided by two inflatable air cushions in the backrest. The desired air cushion is inflated with air or deflated via two solenoid valves until such time that the button for the lumbar-support adjustment is released.

The pump for lumbar-support adjustment delivers the required air pressure. The pump and the solenoid valves are activated from the seat module.

NOTE: Seats with the lumbar support option are generally fitted with a seat module.

The seat adjustment switches are read in from the seat module via the LIN bus.

Front Active Seat

Active seat function can be activated from the status terminal 15 ON with the Active Seat button. The button is located in the armrests of the front door of the vehicle.

The seat module has sole responsibility for this function.

The footwell module requests the button status via the LIN bus and sends this via the K-CAN2. The central gateway transfers the signal to the K-CAN. This allows the seat module to receive the button status. The seat module evaluates the button status. If there is a request to switch on the active seat, then this is executed by the seat module.

Fig. 103: Identifying Button Block In Armrest Of F01/F02 Driver's Side

COMPONENTS DESCRIPTION CHART

1. Passenger assist button
2. M button
3. Button 1
4. Button 2
5. Active Seat button

A powerful pneumatic pump is used for the active seat and lumbar support functions. The pump supplies the air cushion, for the lumbar support and the active seat with the required volume of air. For this reason, the pump is somewhat larger than that which is found in a vehicle without the active seat option.

NOTE: Lumbar-support adjustment has priority over the active seat. For lumbarsupport adjustment, the pump for lumbar-support adjustment runs at maximum speed. For the active-seat function, the pump for lumbar support adjustment runs at roughly half this speed.

Fig. 104: Identifying Button Block In Armrest Of F01/F02 Front-Passenger's Side

COMPONENTS DESCRIPTION CHART

1. M button
2. Button 1
3. Button 2
4. Active seat button

If, after terminal 15 OFF, the seat module receives the status terminal 15 ON within 15 minutes, then the last selected function that was activated will come into operation.

System Overview

Fig. 105: Basic Activation Of F01/F02 Active Seat System Diagram

COMPONENTS DESCRIPTION CHART

1. Lower air cushion, left
2. Upper air cushion, left
3. Upper air cushion, right
4. Lower air cushion, right
5. Output, lumbar-support adjustment
6. Solenoid valve, changeover, active seat/lumbar-support adjustment
7. Pump for lumbar-support adjustment/active seat
8. Footwell module (FRM)
9. Active seat buttons with function indicator
10. Central gateway module (ZGM)
11. Driver's seat module (SMFA)
12. Distributor module, active seat
13. Air supply, active seat

K-CAN - Body CAN
K-CAN2 - Body CAN2
LIN-Bus - Local Interconnect Network bus

K-CAN signals at the seat module

K-CAN SIGNALS CHART

Four air cushions are integrated in the seat surface for the active seat. Two air cushions, one on top of the other, are used in both the left and right seat halves.

The air cushions are inflated with air supplied by the pump for the lumbar-support adjustment. A solenoid valve is integrated in the pump unit. The function of the solenoid valve is to change over the air supply. This ensures that only one function (lumbar support adjustment or active seat) is ever executed.

A distributor module is available for inflating the air cushions. The seat module delivers power to the distributor module as soon as the active seat is switched on.

The distributor module houses a motor, which drives an eccentric shaft. The rotation of the eccentric shaft causes the air inlets to the seat cushions to open or close.

The seat cushions are alternately inflated or deflated, depending on the position of the eccentric shaft. The air inlets are closed when the system is switched off and in the breaks between inflation or deflation.

A switch contact is integrated in the distributor module to switch on the pump for lumbar-support adjustment.

The rotation of the eccentric shaft actuates the contact, which thereby signals activation to the seat module. The seat module switches on the pump for lumbar-support adjustment and changes over the solenoid valve to inflation of the seat cushions.

Undervoltage

If the function fails due to undervoltage when the active seat is switched on, the active seat must be calibrated.

The function does this by itself. The seat cushions are completely deflated the next time the active seat is switched on. The active-seat function is then ready for operation again.

Suspension of functions

In the interest of avoiding irritation when cornering at high speed, the active-seat function is stopped immediately in the event of excessive lateral acceleration.

The lateral-acceleration signal comes from the yaw-rate sensor. The Integrated Chassis Management issues the signal via the FlexRay.

The central gateway module transfers the signals to the K-CAN. This allows the seat module to receive the signal for the vehicle's lateral acceleration. The seat module cancels activation when a defined threshold is exceeded. The function indicator however remains lit.

The active seat is switched on again when the lateral-acceleration value drops again.

Power management

Power management is capable of briefly stopping the active seat from functioning. The function indicator however remains lit.

This applies, for example when pressing the starter or to maintain a sufficient energy balance for the vehicle's electrical system.

System faults

In the event of a system fault, the system shuts down or stops in the next center position in order to avoid further damage. A fault memory entry is stored in the seat module.

Active Seat Ventilation

The active seat ventilation option provides the occupants with individual climate control for the seat and backrest surfaces.

Active seat ventilation is available for both the driver's and front-passenger seats. Active seat ventilation can be activated from the status terminal 15 ON.

Stage 3 is engaged when the button is pressed for the first time. This sets the maximum fan stage for seat and backrest.

The next stage lower or OFF is selected on further pressing of the button. Active seat ventilation is deactivated if the button remains pressed for longer than 1.2 seconds.

Fig. 106: Identifying Button For Active Seat Ventilation

COMPONENTS DESCRIPTION CHART

1. Button for active seat ventilation, driver's seat
2. Button for active seat ventilation, pass seat

The button for the active seat ventilation is located in the IHKA/audio control panel. The seat module has sole responsibility for this function. The integrated automatic heating and air conditioning system evaluates the signals for operating the active seat ventilation and sends the button status to the seat module. This allows the seat module to receive the request, activate the fan and monitor their operation.

Depending on the heating stage, the seat module sends the request for the function to be indicated in the button LEDs to the integrated automatic heating and air conditioning system.

Nine fans are accommodated in each seat. The fans are switched on by the seat module and activated separately for backrest and seat surface. For active ventilation, the seat has two speed stages for the fans, depending on the air-conditioning stage. The seat surface has five fans, while the backrest has four fans.

Seat ventilation stages:

SEAT VENTILATION STAGE

After having been activated for a period in excess of 10 minutes, active seat ventilation is automatically switched down from Stage 3 to Stage 2.

The activated seat ventilation function remains stored for up to 15 minutes after the status terminal 15 OFF. The previously selected seat ventilation stage is switched on again if in this time the status terminal 15 ON is received by the seat module.

The energy management system in the vehicle can deactivate active seat ventilation briefly depending on the vehicle's energy balance. The function indicator is retained however.

Rear Basic Seat

The standard rear seat for the F01 is the basic seat. Seat heating is available for the rear seat as part of the "Luxury seating package".

The rear basic seat offers seating for three people. The seat in the middle is fitted with a folding head restraint.

Fig. 107: Identifying Rear Basic Seat

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