Yes, you can lock and unlock the trunk with the key. The only feature you're missing is being able to open the trunk without the key when the doors are unlocked. Only you can decide if that feature is worth $26 for a new vacuum pod. I did it on my 240D and find it quite handy.

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Rick Miley
2014 Tesla Model S
2018 Tesla Model 3
2017 Nissan LEAF
Former MB: 99 E300, 86 190E 2.3, 87 300E, 80 240D, 82 204D Euro
Chain Elongation References