The auto lock can be turned on by doing this:-

Auto motion lock:
1. Turn on ignition till dash lights come on but don't start engine!
2. Lock the door using the lever on the door handle and then unlock 3 times
3. Turn off ignition
4. Repeat 2 but with ignition OFF
5. Turn on ignition - should hear a beep
6. Lock door again as in 2 BUT ONLY ONCE - final beep should be heard
7. Done!