Truck lost power

[Christian11]

I have a 2012 gmc sierra and was driving it home last night and on my way it cut out and lost power. The locks started to lock on there own and the lights flickered. The engine lost power but it never cut off completely and it went back to running fine. But later down the road when I cut my bright lights on I noticed it did it again. And I'm wondering if any one could help me or has had this problem before. It seems to happen when I cut the bright lights on. And today I went and got the alternator checked and it was fine and no codes were thrown everything checked out fine on the computer. Thanks for any help

[Doug_Scott]

More than likely a bad ground connection in the system. Remove the two battery cables (do the ground cable first to avoid any chance of welding your wrench to the fender if it slips while undoing the bolt), and carefully inspect the ground cable at the terminals for any white or green craps in there. That is corrosion and will cause many odd errors. Verify all connections are tight and clean as well. Make sure to test the alternator in the same condition the truck was in when the issue happened. Turn all accessories on when testing alternator output as well.