Just checked mine prior to Monday's install. GS911 shows no faults when cycling between all the preload modes and damping cycles. I can also hear the steppers when going through the damping cycles with engine off. So alls good.
Just downloaded the latest beta version for the GS911 and there's now the ability to read the Tyre Pressure Monitors (I need to have a play with that one).
My GS-911 didn't show any faults either. Although to be fair to Revs and Wilbers it had shown signs of failing on a Euro trip but was working when the change was made.
Wilbers apparently make new steppers (according to Wilbers and Revs) but after asking on a number of occasions neither have come back with a price.
Be aware that if you are thinking of changing it may be better to opt warranted BMW original @ £1,200 if you want to be sure of a functioning ESA or opt for non -ESA compatibles at a much lower figure.
So far I have spent £600+ for a non adjustable shock.
Because I often have the wife as a pillion or ride with full luggage, as of today, I regret not opting for an original BMW warranted unit.


and more to show for it