My 'Three Amigos' showed up again this time showing a fault code of 'shuttle valve electrical failure.' This forum has generous very helpful information about troubleshooting and repair of the (if it hasn't happened yet...it will) WABCO brake modulator.
My solution was to buy a used (low milage) brake modulator and replace it/hook it up/bleed the brakes/clear the codes...now no ABS/TC/Hill Descent lights or error codes. Expenses: about $250 (I have access to a great garage...If you own a Disco, you have to have a mechanic close). This is an easy replace.
2000 Disco with 168k.

 

And what will you do when your new, used replacement fails, and they all do?
For $160 in parts and fluids, you could have rebuilt your old one and be assured that it won't fail again during your ownership.

 

Have you tried the abs modulator shuttle valve mod. It is under the disco 2 sticky post

 

Thanks for the reply. I think I will replace the shuttle valve on the one I took out and have it ready. The replacement had 'only' 70k miles on it.
Disco Mike, do you recommend replacing the shuttle valve switch only (in addition to flush/fluids/bleeding, etc.)?