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U1073 Communication Bus Off

The OBD2 code U1073 indicates a communication issue where the vehicle's control module is unable to communicate with another module due to a communication bus being offline or malfunctioning

Definition

The OBD2 code U1073 indicates a communication issue where the vehicle's control module is unable to communicate with another module due to a communication bus being offline or malfunctioning

Common causes

  • Faulty wiring or connectors in the communication bus
  • Malfunctioning control modules
  • Short circuits or open circuits in the bus lines
  • Corrupted software or firmware in the control modules
  • Electrical interference or noise in the communication lines
  • Low battery voltage or poor power supply to modules
  • Faulty or damaged sensors connected to the bus

Common misdiagnoses

  • Faulty ABS module
  • Defective engine control module (ECM)
  • Malfunctioning transmission control module (TCM)
  • Bad wiring or connectors
  • Faulty body control module (BCM)
  • Incorrectly diagnosed sensor issues
  • Powertrain control module (PCM) failure
  • Battery or charging system problems

Troubleshooting steps

  1. 1. Check for Additional Codes

    Use an OBD-II scanner to check for any other trouble codes that may be present. This can provide more context about the issue

  2. 2. Inspect Wiring and Connectors

    Visually inspect the wiring and connectors related to the communication bus (CAN bus, LIN bus, etc.). Look for signs of damage, corrosion, or loose connections

  3. 3. Pay special attention to the connectors on the modules that are involved in the communication

  4. 4. Test the Communication Bus

    Use a multimeter or an oscilloscope to check the voltage levels and signal integrity on the communication bus wires. Ensure that the signals are within the expected range

  5. 5. Check for short circuits or open circuits in the communication lines

  6. 6. Check for Module Functionality

    Identify the modules that are part of the communication network. If possible, test each module individually to ensure they are functioning correctly

  7. 7. If a specific module is suspected to be faulty, consider replacing or reprogramming it

  8. 8. Inspect for Ground Issues

    Ensure that all ground connections related to the communication bus are secure and free of corrosion. Poor grounding can lead to communication issues

  9. 9. Look for Interference

    Check for any aftermarket devices or modifications that may interfere with the communication bus. This includes alarms, stereo systems, or other electronic devices

  10. 10. Perform a Network Test

    Some advanced scan tools can perform a network test to check the integrity of the communication bus. Use this feature if available

  11. 11. Clear Codes and Test Drive

    After performing the above checks and repairs, clear the trouble codes using the OBD-II scanner and take the vehicle for a test drive to see if the code returns

  12. 12. Seek Professional Help

    If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or technician who has experience with automotive electronics and communication systems. By following these troubleshooting steps, you can systematically identify and resolve the underlying issues causing the U1073 code