1999 f150 had a heck of a time getting the pattern down to program it. but it did finally work. First of all,you need to have your prevoiusly programed FOB handy and also the one you are going to program handy. insert the key in to the ignition and turn from off to run "several times" so the dealer said. I think I turned mine atleast a hundered times. anyway, repeat this step until the locks activate, then hit your lock button on your programed FOB, locks will cycle then hit your lock button on your programing FOB, locks should cycle again, and that is it. when locks activate the key needs to stay in run position during procedure. Otherwise, you will have to repeat the pattern again.
I've read that early 2001 Supercrew XLTs did not come equipped with standard remote access (option only). I've also heard tale of salesmen telling cutomers (knowingly or unknowingly) that the fobs were apparently lost but they could get new fobs and program them. Be careful.