Active Body Control (ABC) suspension, function - GF32.50-P-4001R
MODEL 230 as of 1.3.06 with CODE (487) Active Body Control (ABC)
Block diagram active body control (ABC)
System functions
Wake-up input
The ABC control unit is discretely woken by the driver-side SAM control unit. The driver-side SAM control unit receives the required data from the rear SAM control unit via CAN-B.
When the ignition is switched on, wake-up mode is aborted as soon as the engine starts running and the ABC control unit switches to normal mode.
Initial check
The initial check includes all system tests that are run through once after system start. Other checks are also performed, such as test actuations to the output stages.
Since the valve output stages have to be actuated immediately after engine start, they are checked as soon as the system switches to wake-up mode.
The various tests forming the initial check are time-graded and performed according to requirement. All components which are required for the "wake-up mode" functionality must be checked before the wake-up mode becomes active.
The initial check is processed completely at the very latest after the engine has been started. As the output stages are not actuated by the function algorithm during these checks, the initial check must be completed quickly (t < 3 s).
Self-leveling suspension
The driver can switch between normal level (NN), a raised level (EN1) (by 25 mm) and the highest level (EN2) (by 50 mm) depending on the vehicle speed by pressing the level adjustment switch with two function LEDs in the lower control panel control unit.
Aligning chassis
The driver can choose between a comfort-oriented and a sporty performance map by pressing the ABC SPORT switch in the lower control panel control unit.
Lock position
The lock position of the ABC control unit is not activated with a locking switch, instead the software detects any reduction in wheel load e.g. as can occur when a wheel is changed or during assembly operations in service.
The lock position is simply a software flag that prevents actuation of the hydraulic suspension struts. If the lock position has been set by the ABC control unit, the blocking valves are closed and the control valves are no longer actuated. There is no display in the instrument cluster and no fault is stored.
The lock position is deleted automatically by the ABC control unit under certain conditions (e.g. vehicle speed > 0 km/h) and the normal functionality is restored.
Display of fault and system messages
The instrument cluster has a multiple line display for displaying system and fault messages to guide the driver.
The ABC control unit transmits a signal to display the messages. The instrument cluster displays the relevant message. There are three different fault messages with different fault priority classes.
The fault priority classes differ mainly with respect to the various acknowledgment options for the driver. The system can cancel the fault display in the instrument cluster by resetting the relevant bit in the CAN communication block (e.g. if the level is no longer critical).
Description of operation
Change vehicle level
The driver can choose between normal level (NN), a raised level (EN1) and the highest level (EN2) by pressing the level adjustment switch, which is read directly by the lower control panel control unit.
If the vehicle is at the normal level (NN) both LEDs are switched off. The vehicle can be raised to level EN1 by pressing the level adjustment switch. The first LED in the switch is actuated and comes on.
If the level adjustment switch is pressed again, the vehicle is raised to level EN2. Both LEDs are actuated and come on.
Pressing the level adjustment switch again lowers the vehicle to normal level (NN). Both LEDs are switched off. If the vehicle exceeds a defined speed threshold, the raised vehicle level is lowered according to the increasing vehicle speed.
This does not cancel the level selected by the driver. The vehicle level is raised accordingly when the vehicle speed reduces again. The LEDs in the switch remain on to indicate the level previously set.
Vehicle level
Vehicles except code (494)
| EN2 (raised level 2) | + 46 mm |
| EN1 (raised level 1) | + 21 mm |
| NN (normal level) | - 4 mm |
| EN2 (raised level 2) | + 46 mm |
| EN1 (raised level 1) | + 21 mm |
| NN (normal level) | - 19 mm |
Vehicles with code (494)
| EN2 (raised level 2) | + 18 mm |
| EN1 (raised level 1) | + 8 mm |
| NN (normal level) | - 7 mm |
| EN2 (raised level 2) | + 18 mm |
| EN1 (raised level 1) | + 8 mm |
| NN (normal level) | - 19 mm |
If the vehicle exceeds or drops below a specified speed threshold, the vehicle level is lowered/raised:
| 0 km | NN | - 4 mm |
| 65 km | NN | - 4 mm |
| 100 km | NN | - 19 mm |
| 0 km | EN1 | + 21 mm |
| 30 km | EN1 | + 21 mm |
| 140 km | EN1 | - 4 mm |
| 0 km | EN2 | + 46 mm |
| EN2 | + 46 mm | |
| 30 km | EN2 | + 46 mm |
| 60 km | EN2 | + 16 mm |
| 140 km | EN2 | - 4 mm |
| 0 km | NN | - 7 mm |
| 65 km | NN | - 7 mm |
| 100 km | NN | - 19 mm |
| 0 km | EN1 | + 8 mm |
| 30 km | EN1 | + 8 mm |
| 140 km | EN1 | - 7 mm |
| 0 km | EN2 | + 18 mm |
| 30 km | EN2 | + 18 mm |
| 60 km | EN2 | + 4 mm |
| 140 km | EN2 | 7 |
| 140 km | EN2 | - 7 mm |
Change chassis alignment
The driver can change the suspension performance map by pressing the ABC SPORT switch in the lower control panel control unit.
The driver can choose between a comfort-oriented and sporty performance map.
The sporty performance map is indicated by an LED integrated in the switch. Pressing the ABC SPORT switch again switches the suspension performance map from sporty to comfort-oriented, the LED is switched off.
Sensors required for the system functions
The front and rear ABC pressure sensors determine the pressures in the suspension struts and the ABC pressure sensor measures the current system pressure.
The level sensors are required for determining the current vehicle level.
The body acceleration sensors are used for measuring the vertical acceleration of the vehicle body.
The ABC lateral acceleration sensor measures lateral acceleration and lateral dynamics.
The signals from the RPM sensors are required by the system to detect standstill, direction of rotation and wheel speed. The SBC hydraulic unit reads the RPM sensor values and transmits them to the ABC control unit over a special CAN bus (CAN-SBC).
The steering angle sensor supplies the steering angle to the system. Together with the ABS wheel speed signal, the steering angle is used to determine lateral acceleration and define the articulation criteria. The steering column module transmits the data telegram to the ABC control unit over a CAN-C interface.
The stop lamp switch detects actuation of the brake pedal and transmits a signal directly to the SBC hydraulic unit. The signal is relayed from there to the traction systems control unit via "CAN-SBC" and then on to the ABC control unit via CAN-C.
The door contact switch (left/right) signals an open driver door. This signal is read by the rear SAM control unit and transmitted to the driver-side SAM control unit via CAN-B. This wakes the ABC control unit over a direct connection.
The pawl rotary tumbler switch signals an open trunk lid and is read by the rear SAM control unit. The signal is transmitted over CAN-B to the driver-side SAM control unit and wakes the ABC control unit over a direct connection.
| ABC suspension strut, component description | GF32.50-P-2001R | ||
| ABC suction restrictor valve, component description | GF32.50-P-4101R | ||
| ABC front axle valve unit, component description | GF32.50-P-4202R | ||
| ABC rear axle valve unit, component description | GF32.50-P-4203R | ||
| ABC central reservoir, component description | GF32.50-P-4221R | ||
| ABC comfort and sport switch, component description | GF32.50-P-4231R | ||
| ABC level adjustment switch, component description | GF32.50-P-4233R | ||
| ABC control unit, component description | GF32.50-P-4501R | ||
| Front/rear ABC pressure sensor, component description | GF32.50-P-4601R | ||
| ABC pressure sensor, component description | GF32.50-P-4602R | ||
| ABC body acceleration sensor, component description | GF32.50-P-4622R | ||
| ABC level sensor, component description | GF32.50-P-4623R | ||
| ABC lateral acceleration sensor, component description | GF32.50-P-4624R | ||
| ABC oil reservoir, component description | GF32.50-P-4625R | ||
| Steering angle sensor, location/task/design/function | GF42.45-P-4600C | ||
| Tandem pump, location/task/design/function | GF46.30-P-3300A |