Fill, there is a relay in the compressor enclosure in the spare tire well. I just figured my issue out on my wagon. These are basically the same systems on the E39 and the E53. See my thread here.
https://www.bimmerforums.com/forum/s...air-suspension
I figured out that once the code was set, which you can tell if the warning comes on as soon as you start the car instead of a delay, than you have to clear it before the pump will come back on. With the warmer temps we are having, you should be able to this resolved.