[urq] an ABS issue?

[spot.ontheroad]

Afternoon/evening all. My apologies for the non-urq content but it is an Audi problem.
My good lady's 1993 Audi 100 Avant has a braking issue which I am trying to solve. The problem is constant pulsing through the brake pedal whenever the pedal is applied - just as if the ABS is engaging all the time. My immediate thought was warped discs (rotors) so I bought some new ones. The old ones were less than 1 year old and I presumed they must have been inferior quality and had warped. Anyway the new (brembo) discs have made no difference at all. There is still a constantly pulsing pedal.
My thoughts are now that it is an ABS issue not a disc problem. There is no provision on this car to turn off the ABS as far as I know.
I intend to remove the fuse that handles the ABS and see if the pulsing goes away.
If it does - it points to it being an ABS problem for sure, but what do I then check and how?
If I pull each wheel sensor out one at a time, is it possible to tell whether or not it is functioning perhaps by testing resistance?
Can a wheel bearing problem cause this. We have the beginnings of a wheel bearing whine but I can't tell which front wheel it is. There does not seem to be any wheel bearing "play" yet in either wheel.
Any suggestions of diagnosis methodology and possible fix will be greatly appreciated.

Many thanks


Keith

'87 WR