Replacing batteries on 2015 Chevrolet Duramax 3500HD LTZ
From my experience these truck give virtually no warning if your batteries are getting weak. The only little warning I got was a no start remote start.
After 6 start and shutoff cycles in the driveway I later went out to a dead truck. Jumpstart and tester told me batteries were done.
I started with the drivers side. Remove terminals and clean if needed. Terminal nuts are 10mm and the wedge bolt is 13mm.
Next remove wedge clamp on front side bottom of battery box.
Remove old battery.
Install new battery and reconnect.
Move on to passenger side.
Remove plastic covers to expose wiring connections. Just a flat blade screw driver to pop the covers off.
The next steps are easier if you remove the fender brace above the battery (3-13mm bolts)
Remove terminals and all other connections.
They are numbered so it’s easy to reinstall. Use a flat blade screw driver to pop the blue connectors out.
Remove plastic wire manifold
Remove old battery and replace with new one. Tighten the wedge bolt before you proceed. Reconnect the terminal manifold before you hook up the positive and negative terminals.
Once everything is snugged you reinstall the fender brace.
I did things in this order and all my settings remained unchanged.