A failure of the self-leveling rear air spring compressor occurred while driving through parking lot. "service rear leveling system" warning was not activated / displayed as published in vehicle owners manual nor did any audible alert sound, notifying driver of any impending problem. as the rear end of the vehicle proceeded to pass over a speed bump at idle speed, the automobile subsequently "bottomed out" leading to significant spine injury. automobile was un-driveable after incident and was taken to the dealership for repairs via flat bed truck. after suspension compressor was replaced, the automobile continued to have audible creaking in rear suspension while traveling over bumps and dips in the road. both l and r shocks were replaced after first being inspected and adjusted per gm/cadillac repair protocol as reported by dealership.