Mercury Mountaineer 2009 Owner's Manual page 586

Locks and Security
5. Turn the ignition from the 1 (off) position to the 3 (on) position. Keep
the ignition in the 3 (on) position for at least three seconds, but no more
than 10 seconds.
6. Turn the ignition to the 1 (off) position and remove the second
previously programmed coded key from the ignition.
7. Within twenty seconds of turning the ignition to the 1 (off) position
and removing the previously programmed coded key, insert the new
unprogrammed key (new key/valet key) into the ignition.
8. Turn the ignition from the 1 (off) position to the 3 (on) position. Keep
the ignition in the 3 (on) position for at least three seconds, but not
more than 10 seconds.
9. Remove the newly programmed coded key from the ignition.
If the key has been successfully programmed it will start the vehicle's
engine and the theft indicator light will illuminate for three seconds and
then go out.
If the key was not successfully programmed, it will not start your
vehicle's engine and the theft indicator light 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 key(s) programmed.
To program additional new unprogrammed key(s), wait twenty seconds
and then repeat this procedure from Step 1.
156
2009 Mountaineer (mnt)
Owners Guide, 1st Printing
USA (fus)