Electronically Controlled Air Suspension Relay
WARNING: This page is about a different car, the 2007 Cadillac DTS. However, it is still accessible from the selected car via links, so may be relevant.
The air compressor is controlled by the air suspension control module by the use of a relay. The relay and wiring are protected with a 60-amp fuse. The air suspension control module will only activate the compressor relay when the engine is running.