Lumbar adjustment function - GF91.29-P-0008FL

MODEL 212 without CODE 409 (Left/right front multicontour seat) without CODE 432 (Left and right dynamic multicontour seat) 

Fig 1: Lumbar Adjustment Function Block Diagram

Courtesy of MERCEDES-BENZ USA

Function requirements, general 

• Circuit 15R ON or run-on active
• No on-board electrical system limp-home mode
• No overvoltage or undervoltage

Run-on:

If circuit 15R is switched off, the lumbar support can still be set for t = 180 s. If, during the run-on time, the circuits status or the door status is changed, the run-on time starts again.

The status of circuit 15 is sent by the electronic ignition lock control unit via interior CAN to the rear SAM control unit or to the driver seat control unit or front passenger seat control unit.

The door status is recorded by the front door rotary tumbler switch. The respective front door control unit reads in the status of the corresponding front door rotary tumbler switch directly and sends this via interior CAN to the rear SAM control unit or to the driver seat control unit or the front passenger seat control unit.

On vehicles with code (275) Memory package for electrically adjustable front seats, the power is supplied to the lumbar support adjustment control units via the driver seat control unit or front passenger seat control unit. On vehicles without code (275) Memory package for electrically adjustable front seats, the power is supplied to the lumbar support adjustment control units via the rear SAM control unit.

Lumbar support adjustment, general 

In order to provide optimum support for the vertebral column, the backrests on the driver and front passenger seats each contain a lumbar support.

The lumbar support unit consists of the following components:

• Two air cushions
• Lumbar support pneumatic pump
• Lumbar support adjustment control unit

Function sequence for lumbar support adjustment 

The adjustment of the lumbar support is performed via the lumbar support adjustment switch. Pressing of the lumbar support adjustment switch is read in directly by the lumbar support adjustment control unit. The lumbar support adjustment control unit controls the corresponding inflation or deflation of the air cushions via integrated valves. The lumbar support pneumatic pump is directly actuated by the lumbar support adjustment control unit for the compressed air supply. In the respective lumbar support adjustment control unit, pressure sensors are integrated that record the pressure values in the air cushions. The signals of the pressure sensors are read in with code (275) Memory package for electrically adjustable front seats directly by the driver seat control unit or front passenger seat control unit and without code (275) Memory package for electrically adjustable front seats directly by the rear SAM control unit.

With code (275) Memory package for electrically adjustable front seats, the current adjustment of the lumbar support can be stored and called up again together with other adjustments via the memory function.

Detailed information about this can be found in the function description "Electrical seat adjustment (ESA), function".