Codes U0073 and P0300?

U0073: This is a diagnostic trouble code (DTC) for "Control Module Communication Bus 'A' Off." It means that there is a general communication problem on the CAN (Controller Area Network) bus A of your vehicle.

P0300: This code stands for "Random/Multiple Cylinder Misfire Detected."

Here is a guide to help you test the wiring round connections to the engine and it shows how the PCM is wired:

https://www.2carpros.com/articles/how-to-check-wiring

Check out the images below. Let us know what you find.