P32.32-A002-79
A1 | Instrument cluster | N72/5s7 | AGILITY SELECT switch (manual transmission, up to model year 2016) | |
A9/1 | AIRMATIC compressor | N72/5s8 | Vehicle level button (manual transmission) | |
A9/1y1 | AIRMATIC pressure reduction valve | N73 | Electronic ignition switch control unit | |
A26/17 | Head unit | N127 | Drivetrain control unit | |
A40/8 | Audio/COMAND display | Y36/6 | AIRMATIC valve unit | |
A40/9 | Audio/COMAND control panel (except code 446 (Touchpad only)) | Y36/6y1 | Left front level control valve | |
A105 | Touchpad (with code 446 (Touchpad only)) | Y36/6y2 | Right front level control valve | |
B22/7 | Left rear level sensor | Y36/6y3 | Left rear level control valve | |
B22/8 | Left front level sensor | Y36/6y4 | Right rear level valve | |
B22/9 | Right front level sensor | Y51 | Left front axle damping valve unit | |
B22/10 | Right rear level sensor | Y51y1 | Solenoid valve 1, front left | |
B24/3 | Left front body lateral acceleration sensor | Y51y2 | Solenoid valve 2, front left | |
B24/4 | Right front body lateral acceleration sensor | Y52 | Right front axle damping valve unit | |
B24/5 | Left rear body lateral acceleration sensor | Y52y1 | Solenoid valve 1, front right | |
K40/8kR | AIRMATIC relay | Y52y2 | Solenoid valve 2, front right | |
L6/1 | Left front axle rpm sensor | Y53 | Left rear axle damping valve unit | |
L6/2 | Right front axle rpm sensor | Y53y1 | Solenoid valve 1, rear left | |
L6/3 | Left rear axle rpm sensor | Y53y2 | Solenoid valve 2, rear left | |
L6/4 | Right rear axle rpm sensor | Y54 | Right rear axle damping valve unit | |
N3/9 | CDI control unit (diesel engine) | Y54y1 | Solenoid valve 1, rear right | |
N3/10 | ME-SFI [ME] control unit (gasoline engine) | Y54y2 | Solenoid valve 2, rear right | |
N30/4 | Electronic Stability Program control unit | CAN A | Telematics CAN | |
N51/3 | AIRMATIC control unit | CAN C | Engine CAN | |
N72/4 | Left lower control panel | CAN C1 | Drive train CAN | |
N72/4s1 | AGILITY SELECT switch (automatic transmission, up to model year 2016) | CAN HMI | User interface CAN | |
N72/4s2 | Vehicle level button (automatic transmission) | Flex E | Chassis FlexRay | |
N72/4s11 | DYNAMIC SELECT switch (automatic transmission, as of model year 2016) | LIN A3 | LCP LIN | |
N72/5 | Right lower control panel | LVDS | Low voltage differential signal | |
N72/5s6 | DYNAMIC SELECT switch (manual transmission, as of model year 2016) |
AIRMATIC general
The AIRMATIC is the combination of an air suspension with a continuous damper adjustment, in which the dampening is adapted on a wheel-by-wheel basis according to the road surface condition and driving style. After the ignition is switched on the last selected level and the last adjusted damping stage are active.
The system comprises the following subfunctions:
Wake-up mode
Level control
Damping adjustment
System and warning messages
Lock position
Wake-up mode
The AIRmatic control unit is activated (woken up) by the active chassis FlexRay after the vehicle is unlocked in order to check the current vehicle level and correct it, if necessary. The AIRMATIC control unit recognizes a critical condition, for example a too low vehicle level at the front axle in which the full wheel angle can no longer be guaranteed, as an error.
In the instrument cluster, the driver is made aware of this situation by the message "vehicle being raised, please wait". Through the wake-up of the AIRmatic control unit a chronological lead occurs which is used to correct the vehicle level. The waiting time for the level correction is shortened as a result.
Additional function requirements for level control
Engine running
The CDI control unit or the ME-SFI control unit sends the engine running signal via the drive CAN, powertrain control unit, and suspension FlexRay to the AIRMATIC control unit.
Level control
The level control system controls the air suspension individually at each wheel. Under normal operating conditions, the air suspension operates with different pressures depending on the load. The compressed-air supply takes place via the AIRMATIC compressor.
Depending on the selected drive program, the vehicle level is reduced or increased and can also be changed by pressing the vehicle level button in the left lower control panel (automatic transmission) or in the right lower control panel (manual transmission).
Selection of transmission mode
The driver can set the desired drive program via the AGILITY SELECT switch (up to model year 2016) or the DYNAMIC SELECT switch (as of model year 2016).
The signals of the AGILITY SELECT switch (up to model year 2016) or the DYNAMIC SELECT switch (as of model year 2016) are read in by the left lower control panel (automatic transmission) or the right lower control panel (manual transmission). The respective lower control panel transmits the signal to the AIRMATIC control unit via the LCP-LIN, Audio/COMAND control panel (except code 446 (Touchpad only)) or touchpad (with code 446 (Touchpad only)), telematics CAN, head unit, user interface CAN, electronic ignition lock control unit and suspension FlexRay.
The symbol for the selected transmission mode is displayed in the instrument cluster. The current transmission mode settings are also briefly shown in the Audio/COMAND display.
The AIRMATIC control unit sends information to the selected drive program via suspension FlexRay, electronic ignition lock control unit, and user interface CAN to the head unit and to the instrument cluster. The head unit generates the corresponding image data and sends a switch-on request to the Audio/COMAND display via telematics CAN. The image data is transferred via a Low Voltage Differential Signaling (LVDS) line to the Audio/COMAND display.
Selection of vehicle level
At a speed below 80 km/h, the driver can set the vehicle level by activating the vehicle level button in the left lower control panel (automatic transmission) or in the right lower control panel (manual transmission). He can choose between the following vehicle levels:
Normal (for normal road conditions)
Increased (for operation with snow chains or for very poor road conditions)
The signals of the vehicle level button are read in by the respective lower control panel. The respective lower control panel transmits the signal to the AIRMATIC control unit via the LCP-LIN, Audio/COMAND control panel (except code 446 (Touchpad only)) or touchpad (with code 446 (Touchpad only)), telematics CAN, head unit, user interface CAN, electronic ignition lock control unit and suspension FlexRay. The AIRMATIC control unit sends the switch on/off request for the LED in the vehicle level button to the corresponding lower control panel in the opposite way. The LED is switched on when the vehicle is at the increased level. An appropriate message additionally appears in the instrument cluster. The AIRMATIC control unit sends the request to output this message via suspension FlexRay, electronic ignition lock control unit, and the user interface CAN to the instrument cluster.
Adjust vehicle level
By increasing the air pressure in one of the multiple-chamber spring bellows, the vehicle level is increased at the wheel concerned. Conversely, the vehicle level is reduced if air is released from the multiple-chamber spring bellows. The AIRMATIC control unit directly actuates the AIRMATIC compressor via the AIRMATIC relay for the compressed-air supply system.
Additionally, the AIRMATIC control unit correspondingly actuates the AIRmatic pressure reduction valve and the following level control valves in the AIRMATIC valve unit:
Left front level control valve
Right front level control valve
Left rear level control valve
Right rear level valve
The vehicle level is changed in the operating status depending on the vehicle speed. For this purpose, the wheel speeds are recorded by the following sensors:
Left front axle rpm sensor
Right front axle rpm sensor
Left rear axle rpm sensor
Right rear axle rpm sensor
The Electronic Stability Program control unit directly reads in the signals of the rpm sensors and sends the corresponding information via suspension FlexRay to the AIRMATIC control unit.
Vehicle level | Level [mm] | v [km/h] | Comment |
Comfort | 0 | <125 | - |
-15 | > 125 | Raise to 0 mm if below 80 km/h | |
Sport | -15 | - | - |
SPORT PLUS | -15 | - | - |
Higher level | +20 | - | Lower to 0 mm if over 80 km/h and 3 min |
Damping adjustment
The electronically regulated damping system operates fully automatically. In comparison to the conventional suspension, it provides improved driving comfort and driving safety. Damping is set harder or softer by the electronics of the AIRmatic control unit depending on the driving situation. If the sensor system records a sporty driving style for example, the comfortable basic damping becomes harder automatically. The automatic program can be set by the driver via the AGILITY SELECT switch (up to model year 2016) or the DYNAMIC SELECT switch (as of model year 2016) in the left lower control panel (automatic transmission) or in the right lower control panel (manual transmission).
The signals of the AGILITY SELECT switch (up to model year 2016) or the DYNAMIC SELECT switch (as of model year 2016) are read in by the respective lower control panel. The respective lower control panel transmits the signal to the AIRMATIC control unit via the LCP-LIN, Audio/COMAND control panel (except code 446 (Touchpad only)) or touchpad (with code 446 (Touchpad only)), telematics CAN, head unit, user interface CAN, electronic ignition lock control unit and suspension FlexRay.
The symbol for the selected transmission mode is displayed in the instrument cluster. The current transmission mode settings are also briefly shown in the Audio/COMAND display.
The AIRMATIC control unit sends information to the selected drive program via suspension FlexRay, electronic ignition lock control unit, and user interface CAN to the head unit and to the instrument cluster. The head unit generates the corresponding image data and sends a switch-on request to the Audio/COMAND display via telematics CAN. The image data is transferred via a Low Voltage Differential Signaling to the Audio/COMAND Display.
The electronics works continuously within a broadly spread damping performance map. The damping force is adapted individually and automatically at each wheel to the current requirements, the road condition and the driving conditions. As a result, the vehicle rolls smoothly even on poor road surfaces, without impairing driving stability.
The AIRMATIC control unit determines the current vehicle level and the damper speeds by evaluating the signals of the following sensors:
Left front level sensor
Right front level sensor
Left rear level sensor
Right rear level sensor
The AIRMATIC control unit determines the body acceleration and body speed of the vehicle by evaluating the signals of the following sensors:
Left front body lateral acceleration sensor
Right front body lateral acceleration sensor
Left rear body lateral acceleration sensor
Based on the input signals, the AIRMATIC control unit determines the respective optimum damping stage and actuates the following component parts accordingly:
Left front axle damping valve unit
Right front axle damping valve unit
Left rear axle damping valve unit
Right rear axle damping valve unit
Additional function requirements for system and warning messages
Terminal 15 ON
The electronic ignition lock control unit sends the circuit 15 circuit status via suspension FlexRay to the AIRMATIC control unit.
System and warning messages
System and warning messages with safety and system-relevant instructions for the driver are displayed on the instrument cluster.
The AIRMATIC control unit sends the request to output messages via suspension FlexRay, electronic ignition lock control unit, and user interface CAN to the instrument cluster. There are various system and warning messages with different fault priorities, depending on the severity of the fault and the urgency of the request for action to be taken.
If several faults exist at the same time, several fault messages will be output accordingly.
Texts displayed in instrument cluster:
"STOP, vehicle too low", plus an acoustic signal
"Vehicle being raised, wait briefly"
"Fault", no signal tone
The following system message is also displayed in the instrument cluster:
"Vehicle lifts up", no signal tone
Lock position
When raising the vehicle, e.g. using a jack, air would be permanently vented from the spring bellows to lower the vehicle. To prevent this from happing, this reduction in wheel load must be detected automatically and a locking position derived from this. To determine whether the vehicle has been raised, a small amount of compressed air is released. If the level sensors do not detect a change in the vehicle level, the locking position is activated.
The locking position is a pure software function which prevents the actuation of the level control valves (draining process). The locking position is activated by the AIRMATIC control unit though evaluation of the signals of the level sensors. There is no fault entry and no display in the instrument cluster.
At a vehicle speed above 10 km/h, the locking position is canceled automatically. The level control system is then in operation again.
The output stages in the AIRMATIC control unit can be actuated via the diagnosis at any time, irrespective of the locking position.