WOMS
U code network High severity

U1779 Control Module Communication Bus Off

The OBD2 code U1779 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 U1779 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
  • Intermittent electrical issues
  • Software or firmware issues in the control module
  • Low battery voltage or power supply issues
  • Faulty or incompatible aftermarket components

Common misdiagnoses

  • Faulty control module
  • Wiring issues
  • Poor ground connections
  • Corrupted software/firmware
  • Faulty sensors
  • Battery or power supply problems
  • Communication network issues
  • Intermittent connection 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 control modules on the communication bus. Look for signs of damage, corrosion, or loose connections

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

  4. 4. Check Power Supply

    Ensure that the affected control module(s) are receiving the proper voltage. Use a multimeter to check the power supply to the module

  5. 5. Verify that the fuses related to the control modules are intact

  6. 6. Test the Control Module

    If possible, perform a functional test of the control module that is reporting the U1779 code. This may involve using specialized diagnostic tools or software

  7. 7. If the module is not responding, it may need to be replaced or reprogrammed

  8. 8. Check for Short Circuits or Open Circuits

    Use a multimeter to check for short circuits or open circuits in the communication lines (CAN bus, LIN bus, etc.)

  9. 9. Inspect the bus lines for any signs of damage or interference

  10. 10. Look for Interference from Other Modules

    Sometimes, other modules on the bus can cause communication issues. Disconnect other modules one at a time to see if the problem resolves

  11. 11. Update Software/Firmware

    Check if there are any software or firmware updates available for the control modules. Sometimes, communication issues can be resolved with an update

  12. 12. Perform a Hard Reset

    Disconnect the vehicle's battery for a few minutes to reset the control modules. Reconnect and see if the code reappears

  13. 13. Consult Technical Service Bulletins (TSBs)

    Look for any TSBs related to the specific make and model of the vehicle. Manufacturers may have issued guidance on common issues related to U1779

  14. 14. Seek Professional Help

    If the issue persists after performing the above steps, it may be necessary to consult a professional mechanic or technician who has experience with the specific vehicle and its systems. By following these troubleshooting steps, you can systematically identify and resolve the underlying cause of the U1779 code