FORD 2008 Expedition v.1 - Manual (Page 170)

5. Within 10 seconds of removing the second coded key, insert the new
unprogrammed key (new key/valet key) into the ignition and turn the
ignition from the 1 (OFF/LOCK) to the 3 (ON) position [maintain
ignition in 3 (ON) for at least three seconds, 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 this
procedure from Step 1.
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 authorized dealer
to have the new spare key(s) programmed.
2008 Expedition (exd)
Owners Guide (post-2002-fmt)
USA (fus)
Locks and Security
170