HelloCustomerand welcome to justanswer.com,
First it would be great to know what code was stored in the abs system to have a better idea as to the diagnosis. I can send you a link on how to check the code if you would like.
Educated guesses would be anything from an external leak at the abs module or a faulty abs module/control unit assembly
here's the link you will need. let me know what code you have.