WOMS
U code network Medium severity

U0035 Vehicle Communication Bus A (-) High

The OBD2 code U0035 indicates a communication issue on the Vehicle Communication Bus A, specifically that the negative signal is high, which may suggest a fault in the bus system or a problem with one of the connected...

Definition

The OBD2 code U0035 indicates a communication issue on the Vehicle Communication Bus A, specifically that the negative signal is high, which may suggest a fault in the bus system or a problem with one of the connected modules

Common causes

  • Faulty CAN bus wiring
  • Short circuit in the CAN bus
  • Faulty control module
  • Poor ground connection
  • Corroded connectors
  • Intermittent electrical connections
  • Faulty termination resistors
  • Software issues in control modules

Common misdiagnoses

  • Faulty ABS module
  • Defective engine control module (ECM)
  • Malfunctioning body control module (BCM)
  • Wiring issues or shorts in the communication lines
  • Faulty sensors or actuators
  • Power supply issues
  • Corroded connectors or terminals
  • Incorrectly installed aftermarket accessories

Troubleshooting steps

  1. 1. Check for Other Codes

    Start by scanning the vehicle for any additional trouble codes. Sometimes, multiple codes can provide more context about the issue

  2. 2. Inspect Wiring and Connectors

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

  4. 4. Pay special attention to the connectors at the ECM (Engine Control Module) and other modules on the bus

  5. 5. Check for Short Circuits

  6. 6. Use a multimeter to check for short circuits in the wiring. Measure the resistance between the communication wires and ground to ensure there are no unintended connections

  7. 7. Test the Modules

  8. 8. If possible, test the modules on the communication bus to ensure they are functioning correctly. This may involve checking for proper voltage and ground at the connectors

  9. 9. If a specific module is suspected to be faulty, it may need to be replaced or reprogrammed

  10. 10. Inspect the Communication Bus

  11. 11. Use an oscilloscope or a scan tool with live data capabilities to monitor the communication signals on the bus. Look for irregularities in the signal patterns

  12. 12. Check for proper voltage levels on the communication lines

  13. 13. Check for Interference

  14. 14. Ensure that there are no aftermarket devices or modifications that could be interfering with the communication bus. This includes things like alarm systems, stereo systems, or other electronic accessories

  15. 15. Clear Codes and Test Drive

  16. 16. After performing inspections and repairs, clear the trouble codes and take the vehicle for a test drive to see if the code returns

  17. 17. Consult Technical Service Bulletins (TSBs)

  18. 18. Check for any TSBs related to the specific make and model of the vehicle. Manufacturers may have issued guidance on common issues related to the communication bus

  19. 19. Professional Diagnosis

  20. 20. If the issue persists after performing the above steps, consider seeking help from a professional mechanic or dealership. They may have specialized tools and knowledge to diagnose complex communication issues. By following these steps, you should be able to identify and resolve the issue related to the U0035 code