Have someone connect the jumpers to the positive on the engine and just pop the trunk,happened to me when i was changing my battery.

Sent from my MB502 using Bimmer App

you should be able to use the key & unlock the trunk manually. good luck.
cheers,
larry

Yes, just use the key. Put it in the lock cylinder and turn until it opens.

90 deg CCW.

Happened to me. No key cylinder in hatch of wagon so only 2 options. I'm assuming you are asking about the wagon as I believe the sedan has a key cylinder.

1. connect jumpers to + on engine and - to chassis from a battery then pop the trunk
2. climb inside to the back trunk and behind the tool panel, there is a emergency trunk release.

I prefer number 1. Good luck.

I typed in /trunk F3 into the bestlinks and found this, among others.

It might help:
- How to open the hood (1) or trunk manually when you have a dead 12v car battery (1) (2) (3) & how to unlock the older E39 if the key is locked inside the trunk (1) (2)