I recently fixed a non-working ABS in my 1994 940. The simple solution to my problem was found by searching the RWD forum archives, however that solution is not currently in the FAQ:

Symptoms: ABS doesnt work, ABS light on dash is off. Connecting the OBD diagnostic pin to A-3 (ABS) in the OBD test housing resulted in a continuous dimly lit red LED. Pushing the test button caused the dim LED to become brighter while the button was pushed but no diagnostic blinks occurred.

Solution: Fuse 24 in the fuseholder block behind the ashtray was open.

In my case the fuse was missing ! The fuse was missing because last year some plastic broke in the interior dome light and caused a short that blew the dome light fuse. I fixed the dome light at night using one of the spare fuses in the fuse block. What I thought was a "spare" 15 amp fuse in position 24 was actually the ABS system fuse. In my hurry to fix the dome light I thought position 24 was spare because it is oriented horizontally and most of the other fuses are oriented vertically.

So my ABS system was disabled ever since I fixed the dome light. I just realized ABS wasnt working when driving on recent ice and snow. This also explains why the ABS light did not turn on when the rear axle ABS/speedo sensor had an open connection a few months ago.

Mike