There are a numerous sensors related to the automatic tailgate mechanism and the problem may be any of them.A shop with the proper BMW diagnostic equipment should be able to fix the problem in no time.

First make sure the bottom half of the tailgate is slammed shut. Unless it's stuck on something, it's probably an issue with the motor that brings it down.

One more thing I thought I'd throw out there for the tailgate. It doesn't seem to latch if the car is a bit tilted meaning if you're ever on the edge of a driveway apron with 1 side of the car flat and the other not (1 rear wheel hanging lower), it may be more sensitive as far as latching closed automatically - it may pop back open.

Thanks, it's slammed and level. I will make an appointment at dealer (its CPO) and circle back next week.

oh our lovely X's...

Really annoying... and sometimes embarrassing! I have this issue often as well. Freaked me out the first time it happened, thought I was going to be stuck cruising with the gate open! Anyhow, seems to be common from this thread. Like many have said, just ensure your bottom gate is secured. Sometimes that means slamming the sh*t out of it... even if it was never opened. That usually does the trick, even if you have to try it more than once.

But, I've learned to live with it.
:dunno:

After readjusting my lower gate more than a year ago (came misaligned from factory) I don't have to slam it at all. It nicely but firmly closes with gentle push of fingers. That's how its supposed to be by design.
BMW has problems during assembly, that's a fact.

SA when I first got there: "hmmmm, NEVER see these things fail? Very odd? May be covered under cpo....but sign here anyway, that you acknowledge the $130 diagnostic fee if it's not"

me: "sweet"

Fast forward 6 hours, SA: "yep, you were right, the right spindle drive failed, replaced under cpo"

I guess I'm happy as it would have been $600 out of warranty. Did not look like complicated fix but I would have never been able to diagnose myself.

Man, I do love this beast (2008 4.8) but the once a month visits to dealer (last one was on a flatbed) make me scared for cpo expiration!