So, get up one day after a snow storm to move my truck, battery dead on my 2015 Sierra Base. Original battery, didn't think much of it, boosted it, went and bought a new battery.
Next day, new battery is dead again.
Brought it to my local mechanic to troubleshoot the draw. He was noticing a 0.5V drop in 9 hours one day, then dead the following day. Charged again, looked at it at night, the heater controls were lit up, another time the instrument cluster warning lights all lit up. He also saw the dome light turn on by themselves. Prior to that, I had other intermittent issues:
- unlock the door with the key, pushed the unlock button on the door, it would not unlock the others, start the engine, then I can unlock with the door button
- parking brake light on the dash doesn't come on parking brake applied
- would crank for 10 to 15 seconds on cold mornings before starting
Spoke to another mechanic I know, he said the fuse box was the issue, he replaced 4 in the last couple of years. I got it replaced by my mechanic and brought the truck home.
I opened up the old box to see what was going on inside, it was a real mess, all corroded to ******, so pretty confident that was the issue. It's so prevalent that the local dealer keeps them in stock.