I have a 03 Chevy Silverado with a 4.8L, and I?m new to tuning and trying to add timing but it won?t log retard at all. I have it in the channels list in the vcm scanner, and everything graphed, I have bumped the timing stupidly to see if I would get knock and I?m not getting anything I?ve also tapped the block and got nothing. It just says 0.0 at all rpms. Is there something I?m missing HELP PLSSS