ABS systems have a high-pressure pump, an accumulator (To store that high-pressure fluid) and a control unit and wheel sensors.
A GM dealer should be able to run diagnostics on you vehicle (KAAaaching) and tell you exactly which component has failed. Or you can pull the wheels and clean the wheel sensors and check their connectors and hope that’s it…If that’s NOT it, forget about it, it will cost more than your Grand is worth to fix it…