Just bought a 2001 discovery and the abs light is on

 

You need a code reader that will tell you what is wrong. Many of us have ABS amigos, they do the trick for usually about 115 to 150 bucks on sale. There is software and other gear that I do not know about. I think some of it is cheaper, and some of it may be better. But the fact is, you are encountering an error and in order to figure out what is wrong with your truck you need a code reader for that error. Something that will read abs codes, you normal OTC reader will not.