Help Please! I have a 2016 suburban. I had a cel for air/fuel imbalance and I asked dealer to look at it since they were already replacing transmission. They forgot to before disconnecting battery. Then I got p0420 for bank 1 cat bad. They wanted 4k to replace. I went to my “exhaust” guy and he replaced with universal HD weld in cat. When he cut it off, he showed me that the cat looked fine. He didn’t understand how it threw code. Anyway, the code came back on and also a U0074 can bus communication error. I took it to dealer and they said it also threw U0073. They kept it for 4 days tracing every bit of wiring and couldn’t find a fault. They said it had to be ECM. I paid to have ECM replaced and I got the code again. I went to a different shop and had diagnosed as PCM. I paid to replace and program the ECM and I got the U0074 again. I am so deep into repair costs, I’m going out of my mind and do t know who to trust. Any advice?