How do you lock the trunk on a 2015 200?
Review the owner's manual. On many vehicles if you have the key fob near the car the trunk will open.
go to your local hardware store and by a latch and padlock, this will solve your malfunctioning tailgate
Trunk should lock with the doors and or key fob like Bob mentioned. If it doesn't something isn't right, have the dealer check it out. Probably still under warranty.
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