Ford 2005 F250 Owner's Manual page 89

Locks and Security
To deactivate/reactivate the autolock feature using the power door
unlock control
You must complete Steps 1-7 within 30 seconds or the procedure will
have to be repeated. If the procedure needs to be repeated, you must
wait 30 seconds.
1. Insert the key and turn the ignition to the 4 (ON) position.
2. Press the power door unlock control three times.
3. Turn the ignition from the 4 (ON) position to the 3 (OFF) position.
4. Press the power door unlock control three times.
5. Turn the ignition back to the 4 (ON) position. The horn will chirp.
6. Press the unlock control, then press the lock control. The horn will
chirp once if autolock was deactivated or twice (one short and one long
chirp) if autolock was activated. Note: Pressing the power door
UNLOCK/LOCK button again will toggle between activating and
deactivating the autolock feature.
7. Turn the ignition to the 3 (OFF) position. The horn will chirp once to
confirm the procedure is complete.
89