2010 Chevrolet impala LT flex fuel 3.5l v6

I have a 2010 Chevrolet impala lt flex fuel 3.5 v6. I have been without a car since October. First my car started going into limp mode, it would stay running but when I hit the gas nothing happened. I took it to 2 parts houses and they both told me something different. I borrowed a obd2 scanner and every time it would give me a code and I would change said part, another code would come up days later and it still drove the same (limp mode) or rpms higher than normal. Since October, I have changed Map sensor, MAF sensor, camshaft sensor, wiring harness for the camshaft sensor, oil pressure sensor, VVT solenoid, changed the oil and filter, ect. It has always cranked and ran fine until recently and it wouldn't start, even though it has good power. Now its giving me a code (U0100) Lost communication with ecm/pcm "A" ..
I'm not sure what the A is but I did have a code that came back camshaft position sensor open circuit "A" which I changed the sensor and harness. I dont know if I need a Ecm/pcm or a TCU since they both run hand in hand. I truly appreciate any advice or recommendations you can give me. I have done all the work myself with the help of a obd2 scanner and Google. I'm out of options here. Does anyone have a wiring diagram for circuit "A" please.