Lock keys in trunk of BMW M3 - 2003 BMW 325

Use your other key FOB or other keys to open the trunk

You have 3 keys for all your vehicles,I would hope

http://www.m3post.com/forums/showthread.php?t=281724

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It should be in the trunk, passenger's side right quarter panel under a black plastic tray that holds the lug nut wrench.

Typical places for water entering the trunk is from the rubber gasket/seal around the tail light assemblies or the rubber gasket/seal around the edge of the trunk itself.

not real sure on bmw but did you try lowering rear windows first

Use the key to open the door and use the trunk button on the door

I vaguely recall reading something in the owners manual of my '97 328 regarding the trunk and the master key. Something about locking things with the master key so that valets cannot open your trunk with the valet key.
Try unlocking the driver door or the trunk with the master key (the original key that had the LED flashlight in it.

break the lock and replace or try removing the back seat to gain entrance to the trunk and retreve your key

if you have a newer 07 and on, there is a lock cylinder near the trunk grab handle. you will have to kneel down to be able to see it. the mechanical key thats inside the remote will have to be used. a spare/valet key wont work. support your local bmw dealership

If you have recently had the key made, it's possible that it needs to be cut again. If all of the cuts in the key are not exact, it could cause your key to unlock doors, and fit ignition, but sometimes it will not work on other locks such as the truck, glove box, etc. If the key is an original, chances are, it could be one of two things.

Either there is another key that goes to the trunk(perhaps the lock cylinder was replaced at one time, or the actual mechanism inside the trunk is either broken or malfunctioning. If this is the case, you'll most likely have to access the trunk through your back seat to open your trunk and/or look to see what the problem is.

However, if you are not comfortable doing this yourself, then I suggest calling a local locksmith. If you can take the car to them, they should be able to get it fixed rather inexpensively. Hope this helps and have a great afternoon!

James