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U2390 Control Module Communication Bus Off

The OBD2 code U2390 indicates a communication issue where a control module is unable to communicate over the vehicle's communication bus, often due to a fault in the module or wiring

Definition

The OBD2 code U2390 indicates a communication issue where a control module is unable 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
  • Interference from aftermarket devices
  • Software issues or bugs in the control module
  • Low battery voltage or power supply issues

Common misdiagnoses

  • Faulty control module
  • Wiring issues
  • Poor ground connections
  • Corroded connectors
  • Faulty sensors
  • Battery or power supply problems
  • Software issues or updates needed
  • Communication network faults
  • Intermittent electrical connections
  • Incorrectly installed aftermarket components

Troubleshooting steps

  1. 1. Check for Other Codes

    Start by scanning the vehicle for any other diagnostic trouble codes (DTCs). Other codes may provide additional 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 the communication bus. 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 the affected control module(s) are receiving the proper voltage. Use a multimeter to check the power supply to the module

  6. 6. Test the Control Module

  7. 7. If you suspect a specific control module is at fault, you can test it by checking for communication using a scan tool

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

  9. 9. Inspect the Communication Bus

  10. 10. Check the integrity of the communication bus (CAN bus, LIN bus, etc.). Look for short circuits, open circuits, or any other issues that could disrupt communication

  11. 11. Use an oscilloscope to monitor the bus signals if you have access to one, as this can help identify communication problems

  12. 12. Check for Interference

    Sometimes, aftermarket accessories or modifications can interfere with the communication bus. Disconnect any non-factory components and see if the issue persists

  13. 13. Perform a Hard Reset

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

  14. 14. Update Software/Firmware

    If the vehicle manufacturer has released updates for the control modules, consider updating the software/firmware, as this can resolve communication issues

  15. 15. Consult Technical Service Bulletins (TSBs)

    Check for any TSBs related to the specific make and model of the vehicle. Manufacturers may have identified common issues and provided solutions

  16. 16. Seek Professional Help

    If the issue persists after performing these steps, it may be necessary to consult a professional technician or a dealership with specialized diagnostic equipment. By following these steps, you should be able to identify and resolve the underlying issue causing the U2390 code