WOMS
U code network High severity

U2279 Control Module Communication Bus Off

The OBD2 code U2279 indicates a communication issue where a control module is not able to communicate over the vehicle's communication bus, often due to a fault in the module or wiring

Definition

The OBD2 code U2279 indicates a communication issue where a control module is not able to communicate over 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
  • Interference from aftermarket devices
  • Low battery voltage or power supply issues
  • Faulty CAN bus transceiver

Common misdiagnoses

  • Faulty control module
  • Wiring issues
  • Poor ground connections
  • Corrupted software/firmware
  • Faulty connectors or terminals
  • Battery or power supply issues
  • Intermittent communication faults
  • Other communication bus errors (e.g., CAN bus issues)

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 associated with the control modules on the communication bus. Look for

  3. 3. Damaged or frayed wires

  4. 4. Corroded or loose connectors

  5. 5. Signs of water intrusion or other environmental damage

  6. 6. Check Power and Ground

    Ensure that the affected control module has proper power and ground connections. Use a multimeter to verify voltage and ground continuity

  7. 7. Test the Control Module

    If possible, test the affected control module to see if it is functioning correctly. This may involve

  8. 8. Replacing the module with a known good one

  9. 9. Performing a bench test if applicable

  10. 10. Inspect the Communication Bus

    Check the integrity of the communication bus (CAN bus, LIN bus, etc.) for shorts, opens, or other issues. This may involve

  11. 11. Using an oscilloscope to monitor the bus signals

  12. 12. Checking for proper termination resistors

  13. 13. Check for Software Updates

    Verify if there are any software updates available for the control modules. Sometimes, communication issues can be resolved with a software update

  14. 14. Clear Codes and Test Drive

    After performing any repairs or checks, clear the trouble codes and take the vehicle for a test drive to see if the code returns

  15. 15. Consult Technical Service Bulletins (TSBs)

    Look for any TSBs related to the specific make and model of the vehicle. Manufacturers may have known issues and recommended fixes for communication problems

  16. 16. Professional Diagnosis

    If the issue persists after performing the above steps, consider seeking help from a professional mechanic or dealership with advanced diagnostic tools

  17. 17. Document Findings

    Keep a record of all findings, repairs, and tests performed. This can be helpful for future reference or if further diagnosis is needed. By following these steps, you should be able to identify and resolve the underlying issue causing the U2279 code