Mr Gerald37,
I ride an 18 RTL and have exactly the same automatic air ride system you do. I replaced the spring on my rear shock and learned a lot about the system. The system consists (simplified) of the air pump, a bleeder valve, a feedback height sensor on the drive belt side about midway up the swingarm, whichever computer controls it, and the related air bag and tubing to hook it all in. The ride height is calibrated by putting the bike up on a specific length high block (simplified) and informing the computer (via BUDS) that that is maximum height, then repeating with a lower block for minimum height. The computer then does whatever it has to do to maintain the rear of the bike in the same relative position about midway between the 2 setpoints. Add a passenger- air bag inflates to 70-80 PSI to keep the rear properly spaced. When I added the heavier spring I found if you increase the preload and raise the rear of the bike more than about 1/2" from the original position you will get a "Suspension Fault" code which will go away when the bike comes back to more normal ride height.
I know, long winded, but it's an information sharing thing.