In the 1990s, adjustable valve shocks and struts were all the rage. These systems had two or three comfort and sport settings that could be changed with buttons on the dash. These systems played the role of firming up the suspension if the driver wanted a sporty feel while driving.
These systems have evolved to the point where they can actively change dampening characteristics in milliseconds. Active dampening or suspension control systems can be found on luxury Asian and European vehicles. But, some of the larger mainstream SUVs and minivans augment the stability control system, as some of these systems work in conjunction with air ride.
These systems usually go unnoticed until there is a problem or when a message is sent to the instrument cluster, indicating there is a fault with the system. Swapping parts on these systems and using guesswork to diagnose a problem will usually result in an angry customer and an annoyed parts supplier. The key to servicing these systems is proper information and understanding precisely how these systems operate.