Some of the early '04 XE's did not come pre-wired, to check if yours is one of those go to this thread.
Brake Cntroller hook up.
Also check at the rear bumper to see if you have a round plug with 7 wires going to it. It will be on the left frame rail area near the bumper bracket.
If your truck is not pre-wired, they have kits to install the 7 wire plug and it's pretty easy.
Also if it is not pre-wired, just use the universal harness that comes with the Prodigy.