WOMS
U code network Medium severity

U1387 U1387: "Control Module Communication Failure

The OBD2 code U1387 indicates a communication failure between control modules in a vehicle, suggesting that one or more modules are not properly communicating with each other

Definition

The OBD2 code U1387 indicates a communication failure between control modules in a vehicle, suggesting that one or more modules are not properly communicating with each other

Common causes

  • Faulty control module
  • Poor electrical connections
  • Damaged wiring harness
  • Corroded connectors
  • Software issues or bugs
  • Low battery voltage
  • Interference from aftermarket devices
  • Faulty CAN bus communication
  • Grounding issues

Common misdiagnoses

  • Faulty control module
  • Wiring issues
  • Poor ground connections
  • Corrupted software or firmware
  • Faulty sensors
  • Battery or power supply problems
  • Intermittent connection issues
  • Communication network faults (e.g., CAN bus 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, 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 control modules. Look for signs of damage, corrosion, or loose connections

  4. 4. Pay special attention to the wiring harnesses that connect the affected control modules

  5. 5. Check Power and Ground

  6. 6. Ensure that the control modules have proper power and ground connections. Use a multimeter to check for voltage and continuity

  7. 7. If there is no power or ground, trace the wiring back to the source to identify any breaks or shorts

  8. 8. Test Control Modules

  9. 9. If possible, test the affected control modules to ensure they are functioning correctly. This may involve using specialized diagnostic tools or swapping with known good modules

  10. 10. Check for any software updates or reprogramming that may be required for the control modules

  11. 11. Inspect the CAN Bus

  12. 12. The communication between control modules often occurs over a Controller Area Network (CAN) bus. Inspect the CAN bus wiring for damage or shorts

  13. 13. Use a scan tool to monitor the CAN bus for any irregularities in communication

  14. 14. Check for Interference

  15. 15. Look for any aftermarket devices or modifications that may interfere with the communication between control modules. This includes alarms, stereo systems, or other electronic devices

  16. 16. Clear Codes and Test Drive

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

  18. 18. Take the vehicle for a test drive to see if the code reappears. Monitor the vehicle's performance and any warning lights

  19. 19. Refer to the vehicle's service manual for specific diagnostic procedures related to the U1387 code. This may provide additional insights or steps tailored to your vehicle's make and model

  20. 20. Seek Professional Help

  21. 21. 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 troubleshooting steps, you can systematically identify and resolve the underlying issue causing the U1387 code