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U2079Control Module Communication Bus Off

The OBD2 code U2079 indicates a communication issue where a control module is not able to communicate on the vehicle's communication bus, often due to a fault in the module or wiring

Definition

The OBD2 code U2079 indicates a communication issue where a control module is not able to communicate on the vehicle's communication bus, often due to a fault in the module or wiring

Common causes

  • Faulty control module
  • Damaged wiring or connectors
  • Poor ground connections
  • Communication bus short circuit
  • Open circuit in the communication bus
  • Corroded connectors
  • Software issues or firmware corruption
  • Intermittent electrical connections
  • Faulty or incompatible aftermarket parts

Common misdiagnoses

  • Faulty control module
  • Wiring issues
  • Poor ground connections
  • Corrupted software/firmware
  • Faulty sensors
  • Battery or power supply issues
  • Communication network problems
  • Incorrectly installed aftermarket accessories

Troubleshooting steps

  1. 1.Check for Additional Codes

    Use an OBD-II scanner to check for any other trouble codes that may be present. Other codes can provide context and help identify the root cause of the issue

  2. 2.Inspect Wiring and Connectors

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

  3. 3.Pay special attention to the CAN (Controller Area Network) bus wiring, as this is often where communication issues arise

  4. 4.Check for Short Circuits or Open Circuits

    Use a multimeter to check for continuity in the CAN bus wiring. Look for any short circuits or open circuits that could disrupt communication

  5. 5.Check for proper voltage levels on the communication lines

  6. 6.Inspect Control Modules

    Identify the control module that is reporting the U2079 code. Inspect it for physical damage or signs of water intrusion

  7. 7.If possible, test the control module in another vehicle to see if it functions correctly

  8. 8.Check for Software Updates

    Verify if there are any software updates available for the control modules. Sometimes, manufacturers release updates to fix communication issues

  9. 9.Reset the Control Module

    Clear the trouble codes using an OBD-II scanner and see if the code returns. Sometimes, a temporary glitch can cause communication issues

  10. 10.Test the Battery and Charging System

    Ensure that the vehicle's battery and charging system are functioning properly. Low voltage can cause communication issues between modules

  11. 11.Check for Ground Issues

    Ensure that all ground connections for the control modules are secure and free of corrosion. Poor grounding can lead to communication failures

  12. 12.Perform a Network Test

    If you have access to advanced diagnostic tools, perform a network test to check the integrity of the communication bus and identify any faults

  13. 13.Consult Technical Service Bulletins (TSBs)

    Check for any TSBs related to the U2079 code for your specific vehicle make and model. Manufacturers may have specific recommendations for addressing this issue.1

  14. 14.Replace Faulty Components

    If a specific control module is identified as faulty, consider replacing it. Ensure that the replacement module is compatible with your vehicle.1

  15. 15.Seek Professional Help

    If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or dealership for further diagnosis and repair. By following these troubleshooting steps, you can systematically identify and resolve the underlying issues causing the U2079 code