GM Service Manual Online
For 1990-2009 cars only

For vehicles with this feature, this self-adjusting type of level control is fully automatic and will provide a better leveled riding position as well as better handling under a variety of passenger and loading conditions. The system is activated when sufficient weight is added to the vehicle, and will automatically adjust vehicle height thereafter. A hydraulic pump inside each rear shock absorber raises the rear of the vehicle to the proper height, based on inputs from the road surface, while the vehicle is being driven. It takes approximately two miles (3.2 km) of driving for the leveling to complete, depending on the road surface conditions.

If the loaded vehicle is not moved for approximately twelve hours, the leveling system may bleed down to a lower height. This can be especially apparent if a trailer is left attached to a parked vehicle for long periods of time. The vehicle must be driven to re-level the vehicle. If a self-equalizing hitch is being used, the vehicle should be driven approximately two miles (3.2 km) with the trailer prior to adjusting (leveling) the hitch.