tune up. fresh spark plugs(premium). check air intake, and exhaust system(cat/converters could be clogged). clean fuel system. amount of ethanol used in modern gas will clog fuel injectors if not cleaned(fuel additive: ethanol treatment) regularly(any vehicle). do system diagnostics.
I got nothing from GM, I call direct, I even ask to get a wiring diagram and they said for me to go to AutoZone that they had books with some prints in them and maybe it might be in one of them, BIG HELP!! The way I found it was by a fuse being blow and when I change it blowed again. then I took the box out of it seal and found a connection solder bad. You had to look close because the joint was just dull and not bright like all the others. My Chev has 106,000 on and this is only thing that went wrong with it other than normal maintance (oil, tires, (on third set) brakes 2nd set.. Thanks for the help///jerry.. I am a electrian by trade.