BMW 840i xDrive Active Suspension System Control Module Replacement Cost

Active suspension systems on modern vehicles use hydraulic or pneumatic pressure to change the ride height, dampening characteristics, and rigidity of the suspension according the the road surface any precise moment. They will typically use a pump or compressor to send pressurized fluid or air to the suspension on each corner of the vehicle, which will raise or lower the vehicle, or increase and decrease stiffness. In order to control this action, a central computer, the active suspension system control module, will use feedback from pressure sensors, yaw sensors, and ride height sensors to determine when and how the vehicle should react.

The active suspension system control module functions by comparing sensor readings from each corner of the vehicle, speed, throttle application, and a variety of other vehicle sensor readings to determine the best possible position for the suspension is for that moment, and use the compressed air or pressurized fluid to make adjustments. The result is a vehicle that stays level when parked, rolls less during turns, and conforms to the road manners the driver desires. Like other control modules and control units, the active suspension system control module is a small computer which is capable of referencing preset data very quickly during vehicle operation.

Since the active suspension system control module is the brain of the entire system, it can mimic the issues of any one part of the system, or show multiple signs of failure. Symptoms can, but not necessarily, include a service warning light for the suspension, ABS or traction control systems, unexpected suspension adjustments, extreme raising or lowering of the vehicle, or lack of adjustability. These symptoms can exhibit themselves at one or more corners of the vehicle, and may be intermittent or permanent.