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AIRmatic, function - GF32.22-P-0003LE

MODEL 221.0 /1 except CODE (487) Active Body Control (ABC) as of Model Year 2009 up to Model Year 2010 /modification year 08, /modification year 09 model refinement package 

MODEL 221.1 with CODE (Z07) Top protection except CODE (487) Active Body Control (ABC) as of Model Year 2009 /modification year 08 

MODEL 216.3 with CODE (489) AIRmatic (air suspension with continuous damper adjustment) as of Model Year 2009 up to Model Year 2010 /modification year 08, /modification year 09 

Function requirements, general 

AIRmatic system, general 

The AIRmatic system is the combination of an air suspension with automatic damper adjustment.

The aim is to keep the vehicle level constant.

Automatic damper adjustment allows the suspension to be adjusted to the prevailing driving situation.

The direction of movement of the vehicle body is used to determine the suitable level of damping force.

The last selected level as well as the last adjusted damping force stage is active after switching on the ignition.

The AIRmatic system consists of the following subfunctions:

System startup function sequence 

The system is started when bus idle is canceled.

This ensues by unlocking the central locking (ZV) or by opening a vehicle door, the trunk lid being rated as a vehicle door.

The following signals are provided to the AIRmatic with ADS control unit (N51) on the chassis CAN (CAN E):

The signals stored on the interior CAN by the corresponding control units are passed on on the chassis CAN by the central gateway control unit (N93). After the AIRmatic with ADS control unit wakes up the current vehicle level is checked and corrected if necessary. Level control is performed in wake-up mode, e.g. when the vehicle is being loaded and unloaded, without the AIRmatic compressor unit (A9/1) being activated. By activating the AIRmatic with ADS control unit a chronological advance occurs which is used to correct the vehicle level. This reduces the amount of time which passes before level correction is performed, and also increases the availability of the vehicle. If the AIRmatic with ADS control unit detects a critical condition for example, such as a too low vehicle level at the front axle, which means that the full wheel angle can no longer be guaranteed, it transmits the appropriate fault message to the central gateway control unit via the chassis CAN. The central gateway control unit makes it available to the instrument cluster (A1) on the central CAN (CAN F).

As a result of this the message "Please wait for a short time - vehicle is lifting up" is displayed in the multifunction display (A1p13) of the instrument cluster.

IMPORTANT Lifting up out of the critical condition takes place irrespective of the condition of the on-board electrical system. The front SAM control unit with fuse and relay module (N10/1) evaluates the on-board electrical system voltage continuously and interrupts or prevents the lifting process if necessary. Current-intensive consumers are shut down in a fixed sequence until a predetermined minimum voltage is reached again.

Additional function requirements for compressed air supply 

Compressed air supply function sequence 

Under normal operating conditions, the AIRmatic system operates with different pressures depending on the load.

Compressed air is supplied by the AIRmatic compressor unit. Any surplus compressed air which is generated is stored in the AIRmatic central reservoir.

This allows large quantities of compressed air to be made available quickly. This increases the adjustment speed when lifting the vehicle and also permits a control when the engine is switched OFF. If a too low pressure is detected in the AIRmatic central reservoir during driving mode, the AIRmatic compressor unit as well as the AIRmatic central reservoir charge valve (Y36/6y5) are actuated and compressed air is delivered to the AIRmatic central reservoir. If the required pressure is reached, the AIRmatic compressor unit is switched off and the AIRmatic central reservoir charge valve is closed. The function is active as of a speed of v > 40 km/h (when accelerating) and down to a speed of > 20 km/h (when braking). The upper cutoff pressure for central reservoir charging depends on the current atmospheric pressure.

Information on this is provided by the CDI control unit (N3/9) (model 221 with diesel engine) or by the ME-SFI control unit (N3/10) (with gasoline engine) on the chassis CAN. The pressure in the AIRmatic central reservoir is monitored by the AIRmatic pressure sensor (Y36/6b1). The compressed air is distributed via the level control valve unit (Y36/6) to the air suspension bellows of the suspension struts.

The following components are accommodated in the level control valve unit:

Additional function requirements for level control 

Level control function sequence 

Level control is realized by means of 4 suspension struts with integral bellows.

If compressed air is admitted to an air suspension bellows, the vehicle level at the wheel in question increases. Conversely, the vehicle level decreases if compressed air is released via the corresponding level control valve or via the AIRmatic pressure reduction valve (A9/1y1).

To compute the current vehicle level the signals from the following components are read in directly by the AIRmatic with ADS control unit:

By operating the level control switch (S6/2s10) in the cockpit switch group (S6/2) the driver can select between the normal level and raised level, each operation of the level control switch causing a change to another level in each case. The status of the level control switch is read in by the upper control panel control unit (N72/1) via the instrument panel LIN (LIN 1) and provided on the interior CAN. The central gateway control unit makes it available to the AIRmatic with ADS control unit on the chassis CAN. The function indicator in the level control switch is actuated by the AIRmatic with ADS control unit in the opposite direction.

IMPORTANT The values listed in the following of the levels and transient conditions can deviate from each other depending on the variant.

Level:

Transition conditions:

Lock position function sequence 

So that when intentionally lifting the vehicle, e.g. with a jack, compressed air is not drained permanently from the air suspension bellows, in order to lower the vehicle it is required to recognize this reduction in wheel load automatically and to derive a blocking position from it. The blocking position is a pure software product which prevents actuation of the level valves (drain process). If the blocking position is recognized by the AIRmatic with ADS control unit, no display in the instrument cluster and no fault storage takes place. As soon as the ESP control unit (N47-5) makes available information on wheel speeds at the front wheels, the AIRmatic with ADS control unit cancels the blocking position and starts with the level control. The output stages of the AIRmatic with ADS control unit are actuated via diagnosis independently of the blocking position status, i.e. it is always possible.

Additional function requirements for damper adjustment 

Damper adjustment function sequence 

The AIRmatic system has an automatic damper adjustment which works according to the "Skyhook" algorithm. All driving condition data are collected and evaluated in the AIRmatic with ADS control unit and from this the actuation signals for damper adjustment are generated. The damping is adjusted harder or softer depending on the driving situation.

The AIRmatic with ADS control unit reads in the signals from the following components directly to determine the movement direction of the vehicle body:

The following information is provided to the AIRmatic with ADS control unit for evaluating the driving condition:

The AIRmatic with ADS control unit computes the required damping force individually for each wheel from the incoming information.

There are 2 different damper operating modes:

The left front axle damping valve unit (Y51), right front axle damping valve unit (Y52), left rear axle damping valve unit (Y53) and right rear axle damping valve unit (Y54) are actuated directly according to the selected damper operating mode.

Soft damping is selected individually for each wheel (if the degree of vehicle excitation permits this).

If the vehicle excitation exceeds a certain degree, "Skyhook" damping is activated for the appropriate wheel.

If the vehicle excitation has decayed, the system switches back to soft damping.

If the sensor system records a sporty driving style for example, the comfortable basic damping becomes harder automatically.

In the process the control characteristics and control response of the damper adjustment can be influenced by the driver by pressing the transmission mode button (A40/9s8).

The status of the transmission mode button is read in by the upper control panel control unit via the instrument panel LIN and is provided on the interior CAN.

The central gateway control unit makes it available to the instrument cluster on the central CAN. The selection of Comfort, Sport or Manual (Manual not with code (494) USA version) is stored in the instrument cluster. The transmission mode stored previously is selected when the engine is started again.

The status of the stored transmission mode is provided to the AIRmatic with ADS control unit by the central gateway control unit on the chassis CAN.

The damping at all 4 wheels is adjusted soft when the vehicle is at a standstill. Only when a defined minimum speed is exceeded does the system change over to "Skyhook" mode.

IMPORTANT In addition a braking or accelerating process which is starting influences the damper operating mode towards "hard", in order to avoid the pitching tendencies of the vehicle. If system components (e.g. valves or sensors) fail, the system automatically switches back to the fallback level "hard" (de-energized valves).

System and warning messages function sequence 

System and warning messages with handling instructions for the driver can be output via the multifunction display in the instrument cluster.

To output the messages the AIRmatic with ADS control unit transmits corresponding information on the chassis CAN The central gateway control unit makes it available to the instrument cluster on the central CAN.

Fault and warning messages are displayed according to a fault priority.

Texts displayed in instrument cluster:

IMPORTANT Priority classes: F1 = high priority, M1 = low priority. If several faults exist at the same time, several messages can be displayed.

  AIRmatic, location of components   GF32.22-P-0003-05LE 
REFER TO SYSTEM WIRING DIAGRAMS Electrical function schematic for AIRmatic Model 221 PE32.32-P-2050-97SAA
Model 216 PE32.32-P-2050-97CAA 
  AIRmatic, block diagram   GF32.22-P-0003-06LE 
  Instrument cluster, component description A1 GF54.30-P-6000LE
  Front central operating unit, component description A40/9 GF54.21-P-4500LE
  Component description for CDI control unit N3/9
Model 221
With engine 629.9		 GF07.16-P-6000OA
N3/9
Model 221
On engine 642.9		 GF07.16-P-6000OHL
  ME-SFI [ME] control unit, component description N3/10
On engine 272		 GF07.61-P-6000MIS
N3/10
On engine 273		 GF07.61-P-6000MLS
  Front SAM control unit with fuse and relay module, component description N10/1 GF54.21-P-6070LE
  Rear SAM control unit with fuse and relay module, component description N10/2 GF54.21-P-6030LE
  ESP control unit, component description N47-5 GF42.45-P-5118LE
  AIRmatic with ADS control unit, component description N51 GF32.22-P-5108LE 
  Left door control unit, component description N69/1
Model 216.3		 GF72.29-P-4124LA
  Left front door control unit, component description N69/1
Model 221.0 / 1		 GF72.29-P-4141LE
N69/1
Model 221.1
with code (Z07) Maximum protection		 GF72.29-P-4141LES
  Right door control unit, component description N69/2
Type 216.3		 GF72.29-P-4128LA
  Right front door control unit, component description N69/2
Model 221.0 / 1		 GF72.29-P-4142LE
N69/2
Model 221.1
with code (Z07) Maximum protection		 GF72.29-P-4142LES
  Rear door control unit, component description N69/3, N69/4
Model 221.0 / 1		 GF72.29-P-6020LE
N69/3, N69/4
Model 221.1
with code (Z07) Maximum protection		 GF72.29-P-6020LES
  Upper control panel control unit, component description N72/1 GF54.21-P-6040LE
  Component description for EIS [EZS] control unit N73 GF80.57-P-6003LE
  Component description for steering column tube module N80 GF54.21-P-6050LE
  Central gateway control unit, component description N93 GF54.21-P-4170LE
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