System Overview: Notes

Index	Explanation
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 

In/Out	Information	Source/sink	Function
In	Outside temperature	Outside temperature sensor > instrument cluster	Ambient conditions when faults are stored
In	Yaw rate	Yaw rate sensor > Integrated Chassis Management	Suspend active seat function
In	Power management	Digital engine control > Seat module	Brief suspension, in order to maintain enough power in the vehicle electrical system

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.