Trunk latch issues

[ATB88]

I've had my 2002 vert for 7 years now, and it's always had a little quirk in the trunk latch -- more often than not, when I push the trunk open button in the dash, or use the trunk button on the key, it'll sound like it tried but didn't quite succeed in unlatching the trunk. Indeed the indicator in the dash will show the trunk open, but if I go back to lift the trunk lid, it's still half latched and won't open. Once it's in this state, to get it to open I have to either use the key physically in the trunk's keyhole, or be lifting the trunk lid with upward pressure while it's failing to unlatch to get it up. I'd say about 10% of the time, it unlatches successfully no problem. I get a code in the body electronics module related to trunk latch: "3D: Trunk-lid unlocking: mechanism"

To describe the sound it makes when failing: if you take the sound it makes when it succeeds (the sound that any of you normally hear when you open the trunk with a button), it's a single definitive click sound. When mine fails, it basically makes that same sound *twice* (and that double click will be how I know it failed before even getting back there to try and open it).

When the car is unlocked, opening using the button under the trunk lid handle to unlatch the trunk always works no problem.

I've always figured that this was the trunk lock actuator itself, and I recently bought and installed a new one (https://www.fcpeuro.com/products/bmw...mo-v20-85-0034). To my surprise and disappointment, it did not fix the problem, I still get the exact same behaviour as before.

Has anyone else encountered this issue and know what the problem is?

[elrichmeister]

Remove the trim on the trunk to see if any of the wires from the "elephant trunk" loom are shorting. I had weird trunk issues on my 325Ci. Turned out to be some wires shorting on the metal of the trunk.

[Ramo]

My trunk (csl) would also not open 50% of the time. Sometimes it would open, other times it would make the noise that it was unlatching but didn't fully unlatch. One day I was adjusting my trunk to get better fitment and once I was done with the adjustments, I realized that my trunk was opening 100% of the time now. So maybe it was a fitment issue with the latch itself. Maybe it was angled or not perfectly straight which was causing the latch not to fully unlatch sometimes. Might be your issue if it's not wires shorting like elrichmeister said.

[PSUEng]

Based on OPs description, I had the same/similar problem and swapped out the actuator with a new one (OE BMW) and it was fixed. Now, the way this thing aligns to the trunk during install is strange to me (at least with my Toyota/Honda experience) and I'd say it's possible you might not have the "rigging" of the trunk just right. You can try adjusting the rubber stoppers after confirming your actuator installation is correct.

[Cubieman]

I had the same issue when I first installed the CSL trunk in that the actuator would "double click" but not open, I had to hold upward the trunk while using the fob.
All it took was a bit of messing with the fitment via the rubber stoppers on the bottom.

[L0okitzRaj]

I’ve had this issue before as well, my solution was adjusting how the trunk sits with the rubber stoppers on the trunk. I’d screw them out a tad to give it a tad bit more resistance, so when you unlock the trunk it pushes it outta the latch.