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AM WORKING ON A 2016 CHEV IMPALA 3.6 LT. CAME IN WITH BCM CODES. CHECKED POWER AND GROUND ON ALL HARNESS AND REPROGRMMED NEW BCM. NOW WHEN YOU TURN ON THE HEADLIGHTS OR TURN THE KEY TO THE ON POSITION THE TRUNK OPENS. NO CODES. SUSPECT RODENT DAMAGE HOWEVER AT THIS POINT NOTHING HAS BEEN FOUND. HAS ANYONE EXPERIENCED THIS ISSUE AND IF YOU DID WHAT WAS THE RESOLUTION? WHAT AM I MISSING?
Maybe unrelated, but I had a Cadillac that would randomly pop the trunk. It was doing it on purpose as part of a low voltage protocol, so that if the battery is dead, you can still get in the trunk and change it. Car never needed a jump or anything, just sometimes the owner would come out from the store and the trunk would be open.
New battery fixed that one.
What codes or issues led you to replace and program a new BCM?
Did you unplug Connector X5 at the BCM, if so, will Key On or the Headlamps activate the trunk lid? This will rule out the BCM, and point to a short to B+ issue.
Using a testlamp connected to ground with X5 plugged back in and going to the underhood fuse panel remove the trunk lid relay.
Probe pin 30 with the headlamp on and or the Key On, what is the test lamp lit?
Thanks Paul. I test power and grounds on all harness’s, I did not do what you wrote about. Great stuff. To be honest i don’t know a lot about this car long story, but it’s been sitting for more than a year, replaced the battery. Replaced the trunk latch because it would click nonstop. Unplugged it and check power and everything checked out. I did replace and reprogram the BCM and a new key fob. Trunk opens whenever you turn on the headlights or turn the key on
Paul, update on the impala. The relay is on the PCB in the BCM and cannot be tested. Use my power probe connected to the trunk latch a did a wiggle test to see if I got a tone change. No luck. Still checking.
For reference, just had a '16 Impala in the shop with the same issue, trunk opens when park lights illuminate. Trunk latch shares a ground with plate lights and ground wire was broke near left side trunk hinge, causing power from plate lights to backfeed through trunk latch. Hope this helps the next guy
Sorry for the late response. We found a wiring harness that runs throught the trunk hinge and it chaffed the wiring harness because it came loose from its mounted hole and 3 wires were exposed and were touching together. We repaired the harness and remounted the harness to the hinge and everything works! Again sorry for the late response, I was injured and just got back.
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