2 thoughts :
1. When I added an additional fob to my 2001, it took me a few times to get the time sequence correct to go into programming mode. The times in the manual were a bit optimistic. If the maxium of 4 was reached, as whitecrystal1 mentioned, they are all erased upon entering programming mode.
Unlock all doors using the power door lock/unlockcontrol
Insert key and turn the ignitionfrom the 1(OFF/LOCK) to the 3(ON) position and cycle between 1(OFF/LOCK) and 3(ON) eight times in rapid succession (within 10 seconds) with the eighth turn ending in the 3(ON) position.
The locks will cycle to confirm that the programming mode has be enentered.
I found that the 10 Seconds to complete this is a bit long, and it is more like 8 seconds.
-> Try again, really hauling through the cycles, ending in the On position. I felt like my 2001 was more like 6 to 8 seconds, to give you an idea of how fast I had to do it.
2. What is the trim level of the truck ?
2.1. Is the RKE a factory option, or after market like a Code Alarm, which looks like the Ford RKE, but could be a different programming button.