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2015 85D Frunk/Front Trunk Sensor - Diagnostic Assistance?

Recently, I've had an issue where my 2015 85D repeatedly believes the front tunk/frunk is open, but then closed, and open again. This, I believe, is the root cause of the app sending me alerts that the alarm has been triggered. I only had that happen once over the summer, but in the last few weeks it's been happening rather frequently, sometimes multiple times in a day or even several times per hour.

Shortly after I got the car (May 2020) I noticed the car had difficulties sensing that the frunk was closed, but usually a firm push on it helped. I took the liner out and cleaned/lubricated the latch mechanism and unplugged/replugged the wires to the switch (that I assume is the sensor that's failing but am not positive). This seemed to help then, but this time it made no difference.

I recorded a video of the dash display showing that the car thinks the hood is sensed as open and closed repeatedly rather quickly:
I have a service appointment tentatively scheduled for the 30th (soonest I could get into a center even remotely close to me) for this plus some other issues (leaking 4-way valve and passenger-side headlight that seems to have a mind of it's own). If I could troubleshoot just one of these, though, I'd love to save the diagnostic cost and maybe even fix it myself. Any tips or troubleshooting advice would be greatly appreciated.
 

David.85D

Active Member
Oct 29, 2016
1,618
1,391
USA
I’d check the ground points under the frunk tub. When mine was failing I had an intermittent headlight and frequent warnings about the hood being open while driving or the alarm going off… service center replaced the latch sensor which didn’t solve the problem. I found the broken grounds which did solve the problem…
 

David.85D

Active Member
Oct 29, 2016
1,618
1,391
USA
There are photos in this thread.

 
Holy smokes, the symptoms described in the thread you linked are identical (headlight, coolant low, app notification, frunk open/close). I know exactly what I'm doing tomorrow after work (or heck, maybe even during my lunch break). Thank you so much for the lead - I swear I searched and searched but couldn't find the right combination of words to dig that thread up.
 
Verdict: As expected it was the ground stud. On visual inspection it looked fine, even a gentle jiggle with my hand seemed fine. But as soon as I tried to loosen the nut it just fell off. $8 for a drill/tap, $1.19 for a brass bolt, $1.19 for a pack of brass washers and I was back in business. I still do have a leaking 4-way valve, but I can cancel the other parts of my service request. Thank you David.85D for linking to the thread!
 
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