GF32.22-P-4005B Level Control, Function

GF32.22-P-4005B Level control, function
- with CODE (487a) Active body control (ABC)



The active body control (ABC) is a fully supporting suspension system. It maintains the vehicle level constant when the engine is running, irrespective of the load.

This is achieved by the radial piston pump pumping oil through the valve units into the suspension struts until the vehicle level has stabilized.

The vehicle level at the front axle and rear axle is detected in each case by two level sensors and sent to the ABC control module (N51/2). The level at the individual suspension struts is regulated by means of 2 control valves each in the valve units of the front axle and rear axle.

Wakeup function (function duration approx. 1 min.)
The ABC control module (N51/2) is "woken up" with the aid of the remote control, the door contact switches or the switch of the trunk lighting in order to verify the vehicle level at that particular moment and to lower the vehicle, if necessary, to the normal level. It is not possible to raise the vehicle level.

Function with vehicle status "ignition ON"
Same function as for wake-up function, but without a time limit.

Normal function (with engine running and while driving)
When the vehicle is loaded, the ABC control module (N51/2) detects the lowering of the vehicle level by means of the level sensors. By actuating the control valves, oil is constantly pumped into the suspension struts of the wheels in question until the vehicle level has reached the specified level. When the vehicle is unloaded, oil is drained by the same valves into the return flow.

Engine-off function (function duration approx. 1 min.)
After "ignition OFF" the ABC control module (N51/2) detects level changes in order to be able to adjust (lower) the vehicle level if any unloading operation is performed. (Same function as for wake-up function).

Locking position, function
If the control module detects that the load acting on the wheels is reduced when the vehicle is stationary and the engine is switched off, the shut-off valves of the suspension struts are closed. The vehicle therefore remains at the current level. This is essential, for example, when changing a wheel or during repair work (lifting platform).

Vehicle level lowered during idle time
The vehicle level may lower itself after a certain idle time. The change in the vehicle level is still within the permitted range in the following situations:
^ Vehicle level lowered due to temperature differences
If the driver turns off the engine when the ABC system is warm, the oil cools and the volume of oil in the system changes. This change in volume can result in the vehicle gradually lowering itself by up to 20 mm depending on the change in temperature.
^ Vehicle level lowered during prolonged idle time
The vehicle may lower itself gradually and evenly up to 30 mm if the vehicle stands idle for 4 weeks.

If the vehicle is not lowered evenly, this may be due to an internal leak in the system.