Ford 2010 E-150 Owner's Manual page 84

Locks and Security
4. Turn the ignition from the 4 (on) position back to the 3 (off) position
in order to remove the second coded key from the ignition.
5. After three seconds but 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 3 (off) position to the 4 (on)
position (maintain ignition in the 4 (on) position for at least one second,
but no more than 10 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 authorized dealer
to have the new spare key(s) programmed.
84
2010 Econoline (eco)
Owners Guide, 1st Printing
USA (fus)