06 Envoy Denali 4wd - 150k - 5.3l. Under normal driving conditions around 45mph vehicle went into limp mode. Speedo stopped working and Gear Indicator stuck on "1". Limped back home and hooked up my scan tool to see if any pending codes were present as MIL was not on. U0101 Lost Communication with TCM is only thing present. I searched the web for ideas. Checked for obvious signs of broken damaged wires/connectors, all look fine. Pulled apart both fuse blocks to check the traces, all are fine and have continuity. Checked pin 6 and 14 on DTC, reads 60.8ohms. Have continuity on GMLAN from TCM to ECM. Replaced TCM and ECM with both used and Dealer New units and no fix. Changed ignition switch as well. I have traced all grounds and cleaned mounting points. I'm not sure where to go next, any ideas would be greatly appreciated.