Anti- lock brake light


“anti-lock brake code” c1264 i took the car to a local shop and he tested it on his machine and said for some reason the correct amperage is not getting/coming from the rear of the car. he said the alternator is putting out like it should. he said he checked amperage other places and couldn’t find any problem. brakes have 50% life left, no loose wires. i don’t know what else to check. could the battery be going bad?