Someone mentioned that a new ABS module ran something like $1500 dollars. Don't know if there is a similar fix available for GM modules, but a common problem on Volvo Bosch (?) modules is bad/broken solder joints on the circuit board on the incoming DC 12V power connections. You can take them out and fix them yourself if you are handy with soldering, or there a few guys who will refurbish them for less than $100, can't recall who they are, but should be easy to find on a Google search. One of the guys doing this will ship you a refurbished module right away on receipt of payment for the service and will then take yours in return to redo for someone else.