Johnny3Sticks

My 2018 Chevrolet 3500HD is doing this. I took it to the local parts house to have the batteries tested (it wouldn’t start without a jump one morning - three hour drive from home after an overnight job), and one (the auxiliary) tested bad, so I replaced it, but the error still comes up, repeatedly and driving me crazy. I’m about to dive into the wiring from stem to stern if I have to.