No connection to ecm thru the obd2 what can cause this? is ecm 07+ silverado ou100 code?

 

Check fuses would be my first bet. Some fuses are more than one circuit on them.

 

Well we checked that and all fuses seem to be working good the only thing is we checked modules with chevy tech2 computer as per the computer tech2 all module passed except communication with the ecm UO100 so sucks we can’t figured it out and OBD2 port for power and pin6 has 2.5v and pin 14 was low so second step checked all the sensors and they all had 5.0v reference kinda stuck there for now