Circuit/System Description
WARNING: This page is about a different car, the 2009 Cadillac DTS. However, it is still accessible from the selected car via links, so may be relevant.
The automatic level control (ALC) system uses a combination level sensor/module, compressor, and exhaust valve to increase or decrease air pressure in the system to control trim height. Battery voltage is supplied to the exhaust valve and compressor relay. The ALC module controls the ground circuits that activate the exhaust valve and compressor relay which maintain trim height based on the level sensor input voltage.