Yes there should be spring tension, pushing inward on the latch tongue you should feel spring resistance and then it should lock into place.

Pressing the hatch button or the keyfob trunk release button should release the latch.

There is a lot of helpful info on the system floating around here, including diagrams, I recall it involves at least 1 module, and a relay or two in the trunk.

From what I remember there are a few fuses to check in the glovebox and rear, and a relay at the rear as well that you can check by swapping with a neighboring relay.

Mine turned out to be the latch and I was able to repair it, others have had to change out latches, and I recall some had to replace the relay.

It's been a while so I cant really remember, but the info is still here and a search will give you a lot of places to start.

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04 X5 3.0i auto
03 X5 4.6is