WOMS
U code network High severity

U1399 is a manufacturer-specific code that generally indicates a communication issue within the vehicle's network

The OBD2 code U1399 indicates a communication issue within the vehicle's network, typically related to a failure in data transmission between modules

Definition

The OBD2 code U1399 indicates a communication issue within the vehicle's network, typically related to a failure in data transmission between modules

Common causes

  • Faulty wiring or connectors
  • Malfunctioning control modules
  • Poor ground connections
  • Corroded or damaged connectors
  • Intermittent electrical issues
  • Software glitches in control modules
  • Faulty sensors affecting communication
  • Issues with the vehicle's CAN bus system

Common misdiagnoses

  • Faulty wiring or connectors
  • Defective control modules
  • Incorrectly diagnosed sensor issues
  • Battery or charging system problems
  • Software or firmware issues
  • Grounding problems
  • Intermittent electrical faults
  • Issues with the vehicle's CAN bus system

Troubleshooting steps

  1. 1. Check for Other Codes

    Use an OBD-II scanner to check for any additional trouble codes. Other codes may provide more context or indicate which module is having communication issues

  2. 2. Inspect Wiring and Connectors

    Visually inspect the wiring and connectors associated with the affected modules. Look for signs of damage, corrosion, or loose connections

  3. 3. Pay special attention to the CAN bus wiring, as it is critical for communication between modules

  4. 4. Check Battery and Ground Connections

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

  5. 5. Check all ground connections for corrosion or looseness, as poor grounding can lead to communication issues

  6. 6. Test the Modules

    If you suspect a specific module is causing the issue, test it for proper operation. This may involve checking for power and ground at the module and verifying that it communicates correctly with the scanner

  7. 7. Inspect for Short Circuits or Open Circuits

    Use a multimeter to check for short circuits or open circuits in the wiring harnesses related to the communication network

  8. 8. Check for Software Updates

    Some manufacturers release software updates for their ECUs. Check if there are any available updates that may address communication issues

  9. 9. Clear Codes and Test Drive

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

  10. 10. Consult Manufacturer Documentation

    Refer to the vehicle's service manual or manufacturer-specific documentation for any additional troubleshooting steps or specific procedures related to the U1399 code

  11. 11. Professional Diagnosis

    If the issue persists after performing the above steps, consider seeking help from a professional mechanic or dealership with experience in diagnosing communication issues in your specific vehicle make and model

  12. 12. Check for Environmental Factors

    Sometimes, environmental factors such as moisture or extreme temperatures can affect the vehicle's electrical systems. Ensure that the vehicle is in a suitable environment for testing. By following these steps, you can systematically diagnose and potentially resolve the communication issue indicated by the U1399 code