Do what the first responder suggested. Get on to Victor Rocha's website. He diagnoses and rebuilds abs controller units for a fraction of the price it will cost you for a new one. You have abs contoller failure a classic 850 problem (right up there with ac evaporator failure). My failed unit threw all sorts of codes which were bogus and all disappeared when I had my abs controller unit repaired. The problem stems from inadequate soldering of connections in the unit which cannot take the heat generated by the unit and develop cracks in the solder connections. Over time these cracks expand and your abs light will stay on for extended periods of time.

Remove the unit and express mail the unit to Rocha or give to your indy for a new unit. You most likely do not have a functioning abs now.

Dan