WOMS
U code network Medium severity

U0520 ISO/SAE Reserved

The OBD2 code U0520 indicates a communication issue with a reserved ISO/SAE network function, typically meaning that a module is not responding or is not recognized in the vehicle's network

Definition

The OBD2 code U0520 indicates a communication issue with a reserved ISO/SAE network function, typically meaning that a module is not responding or is not recognized in the vehicle's network

Common causes

  • Faulty or malfunctioning control module
  • Communication issues between modules
  • Corrupted software or firmware in the control module
  • Wiring or connector problems
  • Electrical interference or noise in the system
  • Incorrectly configured or incompatible aftermarket parts

Common misdiagnoses

  • Faulty wiring or connectors
  • Malfunctioning control modules
  • Software issues or updates needed
  • Incorrectly diagnosed communication errors
  • Sensor failures unrelated to the code
  • Battery or power supply issues
  • Grounding problems

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 related issues

  2. 2. Inspect Wiring and Connectors

    Examine the wiring and connectors associated with the affected modules. Look for signs of damage, corrosion, or loose connections that could disrupt communication

  3. 3. Check Module Functionality

    Identify the specific module that is generating the U0520 code. Ensure that the module is functioning correctly. If possible, perform a module self-test or check for any internal faults

  4. 4. Verify Power and Ground

    Ensure that the affected module has proper power and ground connections. Use a multimeter to check voltage and ground continuity

  5. 5. Inspect the CAN Bus

    Check the integrity of the CAN bus wiring. Look for shorts, opens, or high resistance in the bus lines. You can use an oscilloscope to monitor the CAN signals for proper voltage levels and signal integrity

  6. 6. Check for Interference

    Ensure that there are no aftermarket devices or modifications that could be interfering with the vehicle's communication network

  7. 7. Update Software/Firmware

    If applicable, check if there are any software or firmware updates available for the vehicle's modules. Sometimes, updating the software can resolve communication issues

  8. 8. Perform a Network Test

    Use a professional scan tool to perform a network test. This can help identify which module is not communicating properly

  9. 9. Clear Codes and Test Drive

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

  10. 10. Seek Professional Help

    If you are unable to resolve the issue, consider seeking assistance from a qualified automotive technician or dealership, as they may have specialized tools and knowledge to diagnose complex communication issues. By following these steps, you can systematically identify and address the underlying cause of the U0520 code