Would like to add another solution with error code 401 (fanuc 0M).
Before this error make us to feel sick every day for more than year!!!
On the drive are five relays. Three of them are powered on in parallel.
110V Coil of one of them was burn out. We replaced relay with new one (we used different size relay, original is very rare)
And now our Fanuc works as new!!!
Thanks to everyone (and of course google :-))) who wrote their solution!!!