Ford 2004 Expedition Owner's Manual page 148

Locks and Security
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.
148
2004 Expedition (exd)
Owners Guide (post-2002-fmt)
USA English (fus)