Theory Of Operation
WARNING: This page is about a different car, the 2013 RAM 1500. However, it is still accessible from the selected car via links, so may be relevant.
The air compressor has an air line which connects the reversing valve to the valve block. The ASCM monitors the pressure this air line when it is pressured. After a time the pressure is checked again to see if there is any pressure loss. Any appreciable pressure loss indicates that this air line has a leak.