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Codes U0073 and P0300?

Tiny
EARL91
  • MEMBER
  • 2009 GMC SIERRA
  • 5.3L
  • V8
  • 2WD
  • AUTOMATIC
  • 120,000 MILES
Please help. Need the engine ground wiring diagram or really the all of the engine wire diagram to the PCM. I'm thinking it has a bad ground or some sort of issue the wiring somewhere. I just can't figure out were. I don't know what wires are what. Please help. Thank you.
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Thursday, November 9th, 2023 AT 8:55 AM

1 Reply

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,493 POSTS
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.
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Thursday, November 9th, 2023 AT 10:38 AM

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