WOMS
U code network Medium severity

U1074 Communication Bus Off

The OBD2 code U1074 indicates a communication issue where the vehicle's control module is unable to communicate with other modules on the communication bus, often due to a fault in the network or a module failure

Definition

The OBD2 code U1074 indicates a communication issue where the vehicle's control module is unable to communicate with other modules on the communication bus, often due to a fault in the network or a module failure

Common causes

  • Faulty or damaged wiring in the communication bus
  • Failed or malfunctioning control modules
  • Poor connections or corroded terminals in the wiring harness
  • Short circuits in the communication lines
  • Interference from aftermarket devices or modifications
  • Low battery voltage or power supply issues
  • Faulty or damaged sensors connected to the bus

Common misdiagnoses

  • Faulty ABS module
  • Defective engine control module (ECM)
  • Malfunctioning transmission control module (TCM)
  • Bad wiring or connectors
  • Faulty body control module (BCM)
  • Incorrectly diagnosed sensor issues
  • Powertrain control module (PCM) issues
  • Battery or charging system 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 additional context for the issue

  2. 2. Inspect Wiring and Connectors

  3. 3. Visually inspect the wiring and connectors related to the communication bus (CAN bus, LIN bus, etc.) for any signs of damage, corrosion, or loose connections

  4. 4. Pay special attention to the connectors at the control modules involved in the communication

  5. 5. Test the Communication Bus

  6. 6. Use a multimeter or an oscilloscope to check the voltage levels and signal integrity on the communication bus wires

  7. 7. Ensure that the bus is receiving the correct voltage and that the signals are within the expected range

  8. 8. Check for Short Circuits or Open Circuits

  9. 9. Use a multimeter to check for short circuits between the communication wires and ground or power

  10. 10. Check for open circuits that may prevent communication between modules

  11. 11. Inspect Control Modules

  12. 12. If the wiring and connectors are in good condition, the issue may lie with one of the control modules

  13. 13. Check for any signs of physical damage or water intrusion in the modules

  14. 14. Perform a Network Test

  15. 15. Some advanced scan tools can perform a network test to check the communication between modules. This can help identify which module is not communicating properly

  16. 16. Reset the Codes

  17. 17. After performing inspections and repairs, clear the trouble codes using the OBD-II scanner and take the vehicle for a test drive to see if the code returns

  18. 18. Check for Software Updates

  19. 19. In some cases, a software update for the vehicle's control modules may resolve communication issues. Check with the manufacturer for any available updates

  20. 20. Consult Technical Service Bulletins (TSBs)

  21. 21. Look for any TSBs related to the U1074 code for your specific vehicle make and model. Manufacturers may have known fixes or recommendations for this issue

  22. 22. Seek Professional Help

  23. 23. If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or technician who has experience with automotive electronics and communication systems. By following these troubleshooting steps, you can systematically identify and resolve the underlying cause of the U1074 code