check the harness down by the ecm. the harness likes to rub on the inside of the fender liner. I had a lbz same code and it was rubbed and turned green down there
you can take the starter out and use a flash light and a pray bar to see if the ring gear moves side to side. there is usually a lot of iron rust dust when there broken
did you check the ground g102 on the driver side of the engine block its the one closer to the front. there is a gm bulletin for those codes and a bad ground at g102