Service Air Suspension...Again!!! HUMTECH

[Planohummer]

1)there's a recalibration out for ECAS module-have your dealer do it. should cost less than $100

2)There's an updated design compressor available.

most common failure is exhaust solenoid or overtemp fault. You can't get parts from GM, gotta buy the whole compressor. The compressors are made by Trelleborg - UK division, they might sell you components.
http://www.trelleborg.com/en/Automotive/