Whats the solution to abs lock up?

Does it release after sitting for a while then lock up again right after brakes are applied? If so I would check the rubber hose going to that wheel cylinder. With brake locked up loosen brake line on wheel cylinder side of hose. If brake releases instantly its probably the rubber hose bad. To double check try it again but this time with brake locked up loosen the rubber hose from the frame side not the wheel side. If brake does not release it's a bad hose. Hope this helps.

Oh something else to check if the above is not it. My fathers truck was doing about the same and it turned out to be brake dust build up on his shoes. Leading edge of one shoe and trailing edge of the other. Cleaned with light sand paper and it operated properly.