Here is part of the article I got it from . Thanks again, Dave
ABS2 differences between models
The same basic ABS2 control unit is used on the K1100 and nearly all 5-speed R1100 models. There was an early version that might have only been used on the R1100RS, then the same unit is used on all ABS2 bikes until Motronic 2.4. The only difference seems to be in the wiring; according to my diagram different bikes have different combinations of pins 9, 10, 22 and 23 grounded. Each unit also has a coding number that supposedly can be read out from the center pin (like the fault codes) when the key is on and the ABS button is pushed (although I cannot get this to happen on my R11RS or R11GS):
Coding Pin 9 Pin 22 Pin 10 Pin 23
+8 +4 +2 +1
R1100R, R850R 12 X X
R1100RT 8 X
R1100GS 4 X
R1100RS (93, 94) 2 X
R1100RS (95-) 1 X
K1100LT 11 X X X
K1100RS 7 X X X
This coding might only apply to the 34 51 2 331 935 ABS unit. Other units can be damaged or will not respond to the recoding.
* 34 51 2 306 300 - early model. Might NOT be usable on bikes other than the R11RS! Superseded by...
* 34 51 2 331 935 - R11RS, R11RT, R11R, R850R, R11GS, K11RS, K11LT (MA2.2)
* 34 51 2 325 868 - Remanufactured version of 2 331 935
* 34 51 2 331 637 - R11S, K12RS, R1150GS, R1200C (MA2.4)
* 34 51 2 333 232 -K12LT
In addition to the wiring harness coding, individual ABS units are internally coded to match the harness. This might happen automatically upon installation of a new unit, but if a used unit is transplanted into a different model, the internal coding will be wrong and this will not correct itself with a simple reset. To the best of my knowledge, correcting this can only be done on the BMW diagnostic computer (where it is a trivial task).
To disable ABS on the R1100GS, you hold the ABS button down whilst turning the ignition on. This should leave one ABS light lit, which will flash as you ride.