First things first.
It's "brake."
Your car has brakes to help you stop it. If something breaks on the brakes, they may not work.
Also, if you search this forum, you'll see that your question has been asked and answered before, but...
Sometimes, the e-brake module will mess up when your car's battery is starting to get weak. You might want to have the battery load tested to see if it needs to be replaced. This is a good possibility if the e-brake sometimes works and sometimes doesn't.
Another thing to check is the plastic parts where the e-brake mechanical cables attach to each of the rear caliper assemblies. Those sometimes break. Also make sure that your rear pads aren't worn too thin and need to be replaced.
Still no joy? There is a TSB out that seems to imply that some of the 2004 e-brake modules are defective and should be replaced.
A good, Ford specific, scan tool can retrieve the diagnostic codes from the e-brake module making it much easier to figure out what is going wrong. (Note that most OBDII scanners can't do this.)
Lastly, the V8s have a message center that literally tells you to apply the main brake and leads you through an e-brake calibrate procedure. The V6s don't have a message center, so what is telling you to "step on the foot pedal and..." ?
