Ford F-150 2005 Owner's Manual page 97

Locks and Security
ignition from the 1 (OFF/LOCK) position to the 3 (ON) position
(maintain ignition in the 3 (ON) position for at least one second, but no
more than ten seconds). This step will program your new key to a coded
key.
6. To program additional new unprogrammed key(s), repeat Steps 1
through 5.
If successful, the new coded key(s) will start the vehicle's engine and the
theft indicator will illuminate for three seconds and then go out.
If not successful, the new coded key(s) will not start the vehicle's engine
and the theft indicator will flash on and off and you may repeat Steps 1
through 5. If failure repeats, bring your vehicle to your dealership to
have the new spare key(s) programmed.
97
2005 F-150 (f12)
Owners Guide (post-2002-fmt)
USA (fus)