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U1199 Lost Communication with Vehicle Control Module

The OBD2 code U1199 indicates a loss of communication with the vehicle control module, suggesting that the module is not responding or is unable to communicate with other systems in the vehicle

Definition

The OBD2 code U1199 indicates a loss of communication with the vehicle control module, suggesting that the module is not responding or is unable to communicate with other systems in the vehicle

Common causes

  • Faulty Vehicle Control Module (VCM)
  • Damaged wiring or connectors
  • Poor ground connections
  • Corrupted software or firmware
  • Faulty communication network (CAN bus issues)
  • Blown fuses
  • Intermittent electrical connections
  • Malfunctioning sensors or actuators

Common misdiagnoses

  • Faulty wiring or connectors
  • Defective vehicle control module (VCM)
  • Malfunctioning body control module (BCM)
  • Issues with the powertrain control module (PCM)
  • Problems with the instrument cluster
  • Faulty sensors or actuators
  • Battery or charging system issues
  • Software or firmware glitches
  • Communication network problems (CAN bus issues)
  • Grounding issues

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, other codes can provide additional context for the communication issue

  2. 2. Inspect Wiring and Connectors

  3. 3. Visually inspect the wiring and connectors associated with the affected control module. 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 control module is receiving the proper voltage. Use a multimeter to check the power supply to the module

  7. 7. Verify that the fuses related to the control module are intact and functioning

  8. 8. Test the Control Module

  9. 9. If possible, test the control module itself. This may involve using a scan tool to communicate with the module or swapping it with a known good module if available

  10. 10. Some vehicles may require specific procedures to reset or reprogram the control module

  11. 11. Inspect the CAN Bus

  12. 12. The communication between control modules often occurs over a Controller Area Network (CAN) bus. Check for any issues with the CAN bus wiring, such as shorts or opens

  13. 13. Use an oscilloscope or a CAN bus diagnostic tool to monitor the bus for proper communication signals

  14. 14. Check for Interference

  15. 15. Look for any aftermarket devices or modifications that may interfere with the vehicle's communication systems. This includes alarm systems, stereo systems, or other electronic accessories

  16. 16. Perform a Network Test

  17. 17. Some advanced scan tools can perform a network test to check the communication between modules. This can help identify which module is not communicating properly

  18. 18. Clear Codes and Test Drive

  19. 19. After performing the above checks and repairs, clear the trouble codes using the OBD-II scanner and take the vehicle for a test drive to see if the code reappears

  20. 20. Consult Technical Service Bulletins (TSBs)

  21. 21. Check for any manufacturer-specific TSBs related to the U1199 code or communication issues. There may be known fixes or updates available

  22. 22. Seek Professional Help

  23. 23. If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or technician who has experience with the specific make and model of the vehicle. By following these troubleshooting steps, you can systematically identify and resolve the communication issue associated with the U1199 code