Good question. On GM's website, this is all I could find:
Q: My vehicle says it has "Autoride." What is this and what does it do?
A: Autoride is a fully automatic system that uses a computer controller and sensors to provide superior vehicle ride and handling under a variety of conditions. The controller monitors vehicle speed, wheel to body position, lift/dive and steering position and sends signals to each shock absorber, independently to provide the optimum ride. Part of this feature is automatic level control, which maintains the proper vehicle height on the rear of your vehicle under a variety of loading conditions. You may hear the air compressor running or the system exhausting air to adjust height when the ignition is turned to on, and for up to ten minutes after it has been turned off. Autoride also interacts with the Tow/Haul mode switch to provide additional control when towing a trailer.
But without wires or tubing, exactly how does it work? Osmosis?