[BMWenthuziast]

Originally Posted by Qsilver7

If you used the correct jump start terminals in the engine bay...and supplied sufficient power...this should allow you to open the trunk using the switch in the driver’s footwell or the remote fob or the trunk Roundel mechanism.

Failure to open (when doing the above) usually occurs when an incorrect grounding point is used. Make sure you’re using the dedicated ground BMW provided and indicated in the owners manual. This should work even when the battery is disconnected unless you also undid the battery safety terminal, too...thus disconnecting the main fuse box from the positive cable that connects the front engine bay terminal to the main fuse box.

See engine bay images below for correct pos/neg engine bay terminals...if you used a bolt on the strut tower or other ground location...this could be the problem...it may not be truly grounded.

The image below shows the positive battery cable connections...and even though the illustration shows an e53 X5...BMW uses the same basic design in newer models since they all have a BST (battery safety terminal). Even if the pos battery cable is removed from the battery...the BST keeps the positive battery cable connected to the vehicle’s fuses & relays (if the BST isn’t blown)...this is why & how supplying power to the engine bay terminals allows the car to be powered even if the battery is removed:

This helped. Thanks!