WOMS
U code network Medium severity

U2935 U2935: "Vehicle Communication Bus Malfunction

The OBD2 code U2935 indicates a malfunction in the vehicle communication bus, which affects the ability of various electronic control units (ECUs) to communicate with each other

Definition

The OBD2 code U2935 indicates a malfunction in the vehicle communication bus, which affects the ability of various electronic control units (ECUs) to communicate with each other

Common causes

  • Faulty wiring or connectors in the communication bus
  • Malfunctioning control modules
  • Corrupted software or firmware in control modules
  • Poor ground connections
  • Short circuits or open circuits in the communication lines
  • Interference from aftermarket devices
  • Damaged or defective OBD-II port
  • Low battery voltage or power supply issues

Common misdiagnoses

  • Faulty OBDII connector
  • Bad ground connections
  • Defective ECM (Engine Control Module)
  • Malfunctioning BCM (Body Control Module)
  • Wiring issues or shorts in the communication lines
  • Faulty sensors or actuators
  • Software glitches or outdated firmware
  • Issues with the CAN bus system
  • Corrupted data from diagnostic tools
  • Interference from aftermarket accessories

Troubleshooting steps

  1. 1. Check for Additional Codes

    Use an OBD-II scanner to check for any other trouble codes that may be present. Sometimes, multiple codes can provide more context for the issue

  2. 2. Inspect the Wiring and Connectors

    Visual Inspection: Look for any damaged, frayed, or corroded wiring and connectors related to the communication bus (CAN bus)

  3. 3. Connector Integrity

    Ensure that all connectors are securely attached and free of corrosion or dirt

  4. 4. Check the Battery and Ground Connections

    Ensure that the vehicle's battery is in good condition and fully charged

  5. 5. Check the ground connections for the modules involved in the communication bus. Poor ground connections can lead to communication issues

  6. 6. Test the Communication Bus

    Use a multimeter or an oscilloscope to check the voltage levels on the CAN bus wires. The typical voltage should be around 2.5V when idle

  7. 7. Look for any short circuits or open circuits in the communication lines

  8. 8. Inspect Modules

    Identify the modules that are part of the communication bus (e.g., Engine Control Module, Transmission Control Module, Body Control Module)

  9. 9. Check for any signs of failure or malfunction in these modules. If possible, perform a module reset or reprogramming

  10. 10. Check for Interference

    Look for any aftermarket devices or modifications that may interfere with the vehicle's communication systems (e.g., alarms, stereo systems, etc.)

  11. 11. Perform a Network Test

    If available, use a professional scan tool to perform a network test. This can help identify which module is not communicating properly

  12. 12. Clear Codes and Test Drive

    After performing the above checks and repairs, clear the trouble codes using the OBD-II scanner

  13. 13. Take the vehicle for a test drive to see if the code returns

  14. 14. Consult Technical Service Bulletins (TSBs)

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

  15. 15. Seek Professional Help

    If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or technician who has experience with your vehicle's specific systems. By following these steps, you should be able to identify and potentially resolve the issue related to the U2935 code