Originally Posted by
blindsquirrel
Are there any interconnects between ECM/TCM, other than sharing CAN wiring? If not, then the old GMPP ECM must have had something different from production OSes in one of the segments that allow the manual trans ECM to read speed over CAN. Usually manual trans ECMs totally ignore VSS CAN inputs (it kinda sounds like that's what is happening now after the ECM/OS change), they don't even have the code bits in them to look for it there, and only look for VSS from a hardwired speed sensor.