WOMS
U code network High severity

U0073 Control Module Communication Bus A Off

The OBD2 code U0073 indicates a communication issue where the control module communication bus A is offline or not functioning properly, preventing modules from exchanging data

Definition

The OBD2 code U0073 indicates a communication issue where the control module communication bus A is offline or not functioning properly, preventing modules from exchanging data

Common causes

  • Faulty control module
  • Damaged wiring or connectors
  • Poor ground connections
  • Short circuit in the communication bus
  • Open circuit in the communication bus
  • Corroded connectors
  • Software issues or bugs in the control module
  • Interference from aftermarket devices or modifications

Common misdiagnoses

  • Faulty ECM (Engine Control Module)
  • Bad wiring or connectors
  • Faulty BCM (Body Control Module)
  • Defective TCM (Transmission Control Module)
  • Issues with the CAN bus system
  • Faulty sensors
  • Battery or charging system problems
  • Software issues or updates needed
  • Grounding issues
  • Faulty aftermarket accessories or modifications

Troubleshooting steps

  1. 1. Check for Other Codes

    Start by scanning the vehicle for any additional trouble codes. Other codes may provide more context or indicate which module is having communication issues

  2. 2. Inspect Wiring and Connectors

  3. 3. Visually inspect the wiring and connectors associated with the control modules on Bus A. Look for signs of damage, corrosion, or loose connections

  4. 4. Pay special attention to the ground connections, as poor grounding can lead to communication issues

  5. 5. Check Power Supply

    Ensure that all control modules on the communication bus are receiving the proper voltage. Use a multimeter to check the power supply to each module

  6. 6. Test Control Modules

  7. 7. If you suspect a specific module is causing the issue, you can test it by disconnecting it and checking if the communication bus returns to normal

  8. 8. If the problem persists after disconnecting a module, the issue may lie elsewhere in the communication bus

  9. 9. Scan Tool Communication

    Use a professional scan tool to check if you can communicate with all modules. If you cannot communicate with a specific module, it may be faulty

  10. 10. Check for Short Circuits

    Use a multimeter to check for short circuits in the communication lines. A short can disrupt communication between modules

  11. 11. Inspect the CAN Bus

    If your vehicle uses a Controller Area Network (CAN) bus, check the CAN bus wiring for continuity and resistance. Look for any breaks or shorts in the wiring

  12. 12. Update Software/Firmware

    Sometimes, communication issues can be resolved by updating the software or firmware of the control modules. Check with the manufacturer for any available updates

  13. 13. Reset the Modules

    After performing repairs, clear the codes and reset the modules. Then, take the vehicle for a test drive to see if the code returns

  14. 14. Consult Technical Service Bulletins (TSBs)

    Check for any TSBs related to your vehicle's make and model that may address known communication issues. 1

  15. 15. Professional Diagnosis

    If the issue persists after performing these steps, it may be necessary to consult a professional technician or dealership for further diagnosis. They may have specialized tools and knowledge to pinpoint the problem. By following these steps, you should be able to identify and resolve the issue causing the U0073 code