If the vehicle can no longer be locked with the SmartKey, you can lock it by taking the following steps. If the central locking in the vehicle is malfunctioning, you cannot lock the trunk.

Press down the locking knobs on the open rear doors.
Close the rear doors.
Open the front-passenger door.
Close the driver's door and the trunk lid.
Press down the locking knob of the driver's door inside the vehicle.
Press down the locking knob of the open front-passenger door.

Make sure that you have the SmartKey on your person and that it has not been left in the vehicle.

Close the front-passenger door.
Make sure that the doors and the trunk are locked.

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