I have a 67 GTO swapped LS3 with a new 6l80e. Runs, moves forward no reverse. Had the trans checked twice. Only code that keeps coming up is P2537. Has a Current performance standalone harness with Tap shift. It seems to read on our scan tool some kind of ignition circuit. The e38 ecm and Tcm are Brand new and flashed with a 2017 Chevrolet SS operating system. Which came with a LS3 and 6l80e. Any help would be great.