Similar problem here....
I took my car (2013) in to get the "Coolant Delete" LDU, so rear subframe was dropped out of the car. When I brought it in, air suspension was working perfect.
Within 5 minutes, on the drive home at highway speed, I got the yellow suspension light on the dash, and the rear passenger wheel was slammed low.
I got the compressor to work, and the system held air overnight, so no leaks. I also verified no leaks with a tire gauge on the Schrader valve for the system air tank.
I just replaced the ride height sensor on the rear passenger wheel, and it's better, but the car rides with the front driver's wheel at a higher level, and the passenger's rear wheel at a lower level than the ride height setting.
Shop that did the LDU work says that they didn't touch the suspension, and that it is coincidental.
No errors in Service mode.
I performed other service (clean the contacts on the DC DC converter) that required disconnecting the 12V and fireman's loop. No change.
1) Would Toolbox be helpful here? Do you suggest paying a shop to connect the car to Toolbox?
2) Does dropping the subframe involve messing with the air suspension?
3) What would happen if the mechanic did not put the car in "Jack Mode"?
4) Has anyone converted their air suspension car to regular spring coil struts?
5) Is there a way to electrically check the ride height sensors for proper operation prior to replacement?
Brian