2016 Duramax cold start electrical issue

[Per_Haugland]

I was wondering if anyone has had this issue and knows what causes it. My 2016 Duramax won’t start cold, it clicks and the dash/lights go dark. Both batteries are at about 12.75 volts and load test fine. I checked all the connections power and ground and everything is tight and clean. Eventually it starts up.  My truck is a month out of warranty of course so before I go to the shop wanted to see if there was an easy fix. I think the starter itself is still covered under powertrain. THanks!