With the little information you have given me, it is hard to say. The fact that you cannot communicate with the ECM tells me you either have an issue with the serial data line or the ECM itself.
I would address this issue first as it may be the source of your issue. You need to unplug one module at a time and watch to see if you can communicate with any module. Time-consuming procedure but must be done before you can point a finger anywhere as to the failure. Is the check engine light on?
I do not like to guess and I know you have had a lot of recommendations but you need to start with basics to find the issue.
Check pin 16 in your connector under the dash for power.
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Wednesday, June 2nd, 2021 AT 12:40 PM