The U code is for no communication with the ECM. That would explain why it will not start.
Can you read any data with your code reader?
This is not a ground issue at all.
Do you have a volt meter to do some checks at the data link connector?
Roy
We located the ECM and performed some circuit test on the CAN data lines. We found that the wiring and connectors were good. We checked for 2.5 volts at pin 6 and 2.25 volts at pin 14 of the DLC. We also checked PIN 7 through the ECM to the DLC. We found that the ECM was not sending the correct outputs. We decided to replace the ECM with a used unit. We installed the used ECM and programmed it. We rechecked and the vehicle established communication with the scan tool and the DTC is gone.
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Tuesday, May 25th, 2021 AT 5:34 PM
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