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U code network Medium severity

U1938 U1938: "Module Communication Failure

The OBD2 code U1938 indicates a "Module Communication Failure," meaning there is a problem with communication between vehicle modules, often due to a fault in the wiring, connectors, or the modules themselves

Definition

The OBD2 code U1938 indicates a "Module Communication Failure," meaning there is a problem with communication between vehicle modules, often due to a fault in the wiring, connectors, or the modules themselves

Common causes

  • Faulty wiring or connectors
  • Failed or malfunctioning control module
  • Poor ground connections
  • Corroded or damaged pins in connectors
  • Communication network issues (e.g., CAN bus problems)
  • Software or firmware issues in modules
  • Intermittent electrical connections
  • Low battery voltage or power supply issues

Common misdiagnoses

  • Faulty wiring or connectors
  • Defective control modules
  • Software issues or updates needed
  • Power supply problems
  • Grounding issues
  • Intermittent communication faults
  • Incorrectly configured or programmed modules

Troubleshooting steps

  1. 1. Check for Other 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 Wiring and Connectors

  3. 3. Visually inspect the wiring and connectors associated with the affected module(s). Look for signs of damage, corrosion, or loose connections

  4. 4. Pay special attention to the ground connections, as poor grounding can lead to communication issues

  5. 5. Check Power Supply

  6. 6. Ensure that the affected module is receiving the proper voltage and ground. Use a multimeter to check the power supply to the module

  7. 7. If the module is not receiving power, trace the wiring back to the fuse box and check for blown fuses or damaged wires

  8. 8. Test the Module

  9. 9. If possible, test the affected module to ensure it is functioning correctly. This may involve using specialized diagnostic tools or swapping the module with a known good one

  10. 10. If the module is faulty, it may need to be repaired or replaced

  11. 11. Check for Communication

  12. 12. Use a scan tool to check if the affected module is communicating with other modules. If it is not, there may be a fault in the communication network

  13. 13. You can also use a scope or a multimeter to check the data lines for proper signals

  14. 14. Inspect the CAN Bus

  15. 15. If your vehicle uses a Controller Area Network (CAN) bus, check for issues with the bus itself. Look for short circuits, open circuits, or interference

  16. 16. You may need to use a CAN bus analyzer to diagnose communication issues

  17. 17. Reset the Codes

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

  19. 19. Consult Technical Service Bulletins (TSBs)

  20. 20. Check for any manufacturer-specific TSBs related to U1938 or communication issues. There may be known fixes or updates available

  21. 21. Seek Professional Help

  22. 22. If you are unable to resolve the issue after these steps, consider seeking help from a qualified automotive technician or dealership. They may have access to advanced diagnostic tools and resources. By following these steps, you should be able to identify and resolve the underlying issue causing the U1938 code