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U002D High Speed CAN Communication Bus Off

The OBD2 code U002D indicates a malfunction in the high-speed CAN (Controller Area Network) communication bus, meaning that the communication between modules is disrupted or offline

Definition

The OBD2 code U002D indicates a malfunction in the high-speed CAN (Controller Area Network) communication bus, meaning that the communication between modules is disrupted or offline

Common causes

  • Faulty CAN bus wiring or connectors
  • Defective CAN bus module
  • Short circuit in the CAN bus
  • Open circuit in the CAN bus
  • Interference from other electrical components
  • Faulty or damaged sensors communicating over the CAN bus
  • Software or firmware issues in the control modules
  • Low battery voltage or poor ground connections
  • Corroded or loose connections in the CAN network
  • Malfunctioning or incompatible aftermarket devices

Common misdiagnoses

  • Faulty ABS module
  • Defective engine control module (ECM)
  • Bad wiring or connectors
  • Malfunctioning body control module (BCM)
  • Issues with the transmission control module (TCM)
  • Battery or charging system problems
  • Faulty sensors (e.g., wheel speed sensors)
  • Incorrectly diagnosed CAN bus issues
  • Software or firmware issues in modules
  • Grounding problems in the electrical system

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 additional context for the problem

  2. 2. Inspect Wiring and Connectors

  3. 3. Visually inspect the wiring and connectors associated with the CAN bus. Look for signs of damage, corrosion, or loose connections

  4. 4. Pay special attention to the connectors at the ECM (Engine Control Module), BCM (Body Control Module), and any other modules connected to the CAN bus

  5. 5. Check for Short Circuits

  6. 6. Use a multimeter to check for short circuits in the CAN bus wiring. Measure the resistance between the CAN High and CAN Low wires; they should not be shorted together

  7. 7. Check for shorts to ground or power in the wiring

  8. 8. Test the CAN Bus Voltage

  9. 9. With the vehicle in the ON position (engine off), measure the voltage on the CAN High and CAN Low wires. The typical voltage levels should be around 2.5V to 3.5V for CAN High and 1.5V to 2.5V for CAN Low

  10. 10. If the voltages are outside this range, there may be a fault in the wiring or a module

  11. 11. Check Termination Resistors

  12. 12. Ensure that the CAN bus has the proper termination resistors (typically 120 ohms) at each end of the bus. A missing or faulty resistor can cause communication issues

  13. 13. Inspect Modules

  14. 14. Check the modules connected to the CAN bus for proper operation. A malfunctioning module can disrupt communication

  15. 15. If possible, disconnect modules one at a time to see if the code clears or communication is restored

  16. 16. Scan for Module Communication

  17. 17. Use a scan tool to check if all modules on the CAN bus are communicating properly. If some modules are not responding, it may indicate a problem with those specific modules

  18. 18. Check for Interference

  19. 19. Look for any aftermarket devices or modifications that may interfere with the CAN bus communication, such as alarms, remote starters, or audio systems

  20. 20. Perform a Network Test

  21. 21. Some advanced scan tools can perform a network test to check the integrity of the CAN bus. This can help identify issues with specific modules or wiring

  22. 22. Clear Codes and Test Drive

  23. 23. After performing the above checks and repairs, clear the trouble codes and take the vehicle for a test drive to see if the code returns. 1

  24. 24. If the issue persists, consult the vehicle's service manual for specific troubleshooting procedures related to the CAN bus for your make and model. 1

  25. 25. Seek Professional Help

  26. 26. If you are unable to resolve the issue, consider seeking help from a qualified automotive technician or dealership, as they may have specialized tools and knowledge to diagnose complex CAN bus issues. By following these steps, you should be able to identify and resolve the issue causing the U002D code