FixItFor.Us
U codenetworkMedium severity

U1520U1520: Body Control Module Communication Error

The OBD2 code U1520 indicates a communication error between the Body Control Module (BCM) and other modules in the vehicle, suggesting a potential issue with wiring, connectors, or the BCM itself

Definition

The OBD2 code U1520 indicates a communication error between the Body Control Module (BCM) and other modules in the vehicle, suggesting a potential issue with wiring, connectors, or the BCM itself

Common causes

  • Faulty Body Control Module (BCM)
  • Poor electrical connections or wiring issues
  • Corroded connectors
  • Faulty or damaged CAN bus wiring
  • Malfunctioning or incompatible modules
  • Software or firmware issues
  • Low battery voltage or power supply problems
  • Interference from aftermarket accessories or modifications

Common misdiagnoses

  • Faulty Body Control Module (BCM)
  • Wiring issues or short circuits
  • Corrupted software or firmware in the BCM
  • Faulty connectors or terminals
  • Issues with other control modules (e.g., Engine Control Module)
  • Battery or charging system problems
  • Grounding issues
  • Faulty sensors related to the BCM
  • Communication network issues (e.g., CAN bus problems)

Troubleshooting steps

  1. 1.Check for Other Codes

    Use an OBD-II scanner to check for any additional trouble codes. Sometimes, related 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 BCM and other modules for any 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 BCM is receiving the correct voltage and ground. Use a multimeter to check the power supply to the BCM

  7. 7.Look for blown fuses that may affect the BCM or related circuits

  8. 8.Test the BCM

  9. 9.If possible, test the BCM for proper operation. This may involve using a scan tool to check for BCM functionality or replacing it with a known good unit to see if the problem persists

  10. 10.Inspect Other Modules

  11. 11.Check the other modules that communicate with the BCM. If one of these modules is malfunctioning, it can cause communication errors

  12. 12.Look for any signs of damage or issues with the wiring harnesses connecting these modules

  13. 13.Perform a Network Test

  14. 14.Use a scan tool capable of performing a network test to check for communication between the BCM and other modules. This can help identify if the issue is isolated to the BCM or if it involves other components

  15. 15.Clear Codes and Test Drive

  16. 16.After performing any repairs or inspections, clear the trouble codes and take the vehicle for a test drive to see if the code reappears

  17. 17.Check for Software Updates

  18. 18.Sometimes, communication issues can be resolved with a software update for the BCM or other modules. Check with the manufacturer for any available updates

  19. 19.Consult Technical Service Bulletins (TSBs)

  20. 20.Look for any TSBs related to the U1520 code for your specific vehicle make and model. Manufacturers may have specific recommendations or known fixes for this issue

  21. 21.Seek Professional Help

  22. 22.If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or dealership for further diagnosis and repair. By following these steps, you can systematically identify and resolve the communication error associated with the U1520 code