I've waited about 30 minutes last time. Basically waited until it fell to the lowest number. Today I'm going to wait a few hours and see what happens. Where can I get a wiring diagram? I've tried the google but no luck

Try this link to Chilton'* that I got off of the Buick Owners club website http://infotrac.galegroup.com/itweb/...oswell?db=CHLL
The password is cactus.

Does your Buick have OnStar? My 2002 Buick Lesabre was losing almost 2 volts overnight with a 46 mv draw. I disconnected the OnStar module and battery is holding steady now.

I think the issue is the bluetooth, but I do not know how to fix it. My wife'* 2014 Verano always lost the battery if it sat for 3 days since the car was brand new. Of course the dealership could never find the problem while under warranty. The car eats batteries due to the issue and worse, makes my wife very unhappy when she want to go somewhere. I decided to try myself and like you I chased it down to the infotainment system intermittently drawing quite a bit of power when the car was off and after it should be asleep. I pulled the fuse and the problem was gone, but obviously the infotainment system didn't work. So I did a reset of the system. I had done that several times before, but this time I did not re-pair my wife'* phone to the bluetooth system. So far I have not had the problem with no phone paired, but she uses that feature often so I want to correct it.

Like you I was thinking maybe a software update would correct it. But I have not been able to find how to download and install the update (although I have done it on cars from other manufacturers). I also once saw a service bulletin on it quite some time ago, but have not been able to relocate it recently. Hopefully this helps and let me know if you find a solution.