2003 Chevy 2500HD Diesel
Try cleaning the ground wire lugs, @ all Locations, that can cause a lot of issues with random things, not allowing a complete circuit to whatever is the problem @ the moment. I had a issue with my transmission going into safe mode, replaced all the shift solenoids, fluid, filter, and so on, then one day driving in the rain, turning on the defrost, turning fan on high, (safe mode) turn fan down on low, shifting fine. Realized I was robbing power from transmission ground, (solution) cleaning all ground points and running a 2 gauge wire to the computer from the battery Negative Have not had a problem since. (About 6 years) Won't hurt anything.