I found the procedure for my 92 Eldorado on caddyinfo.com. My rear struts were bleeding off pretty bad, and I wanted to see if I could turn off the message if I switched to passive struts. It worked for me, and it didn't. T he message didn't come on but since there was nothing wrong with my front struts, disabling the system made the ride much worse. I don't think it's a good idea to mix passive on 1 axle with air on the other.
Plus, NAPA carries replacement air struts for my 92 for $75 each. Passive weren't much cheaper.