Notchpedro

Got a bit of a problem with my 2007 Avalanche 5.3 Got one code: U0100 - Lost comunication with ECM/PCM A. Wont even crank. Also got Service stabilitrak, service traction control, park assist off. Fuel gauge dont move at all, stays at the bottom. (tank is half full) Got 60 ohms at the diagnostic port. Checked the 5V reference points and I got less than 1V on all three. (map sensor, maf and tps) Starter is fine, have removed it and tested it. Have replaced the negative and positive battery cables and have tried with 2 other batteries. Is replacing the ECM/PCM the next step or am I missing something?