Called Allison mechanic told me have to go to gmc dealer have code po700 and U2104 is there anything I can check can these code be set by anything like a filter change or is it in the wiring and without a road map no way to get there from here LOLor

 

P0700 is just the TCM telling the ECM to light the CEL. You would need a better code reader to get the actual code from the transmission. U codes are communication errors between the computer modules, ECM, TCM, FCIM, Etc.

try clearing the codes and see if they come back. If they do look for loose or dirty pins at the ECM, TCM, Etc. Look for bad grounds, wires that have rubbed through. May also be your batteries or ignition switch going bad.