If the vehicle can no longer be locked with the SmartKey, use the mechanical key.

Open the driver's door.
Close the front-passenger door, the rear doors and the trunk lid.
Press the locking button.
Check whether the locking knobs on the front-passenger door and the rear doors are still visible. Press down the locking knobs by hand, if necessary.
Close the driver's door.
Take the mechanical key out of the SmartKey.
Insert the mechanical key into the lock of the driver's door as far as it will go.

Turn the mechanical key clockwise as far as it will go to position 1.
Turn the mechanical key back and remove it.
Make sure that the doors and the trunk lid are locked.
Insert the mechanical key into the SmartKey.

If you lock the vehicle as described above, the fuel filler flap is not locked. The antitheft alarm system is not armed.