'02 DeVille Brakes to the floor, bad ABS???
 

Help, Father-In-law having brake trouble. He told me he was driving and the brake pedle went to the floor. Dealership drove but no issues found. 2nd time, Dealership replaced ABS Module, Booster pump, and electrical control module for ABS. In-law drove home afterwards, and brake pedal back to the floor barely enough to stop. No fluids leaking that he could see. ABS warning light was on both times.
Any thoughts???? Was ABS assembled incorrectly befor installed???? Dealership asked him to call GM phone number given by Shop Manager???