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U1905U1905: "BCM Communication Failure

The OBD2 code U1905 indicates a communication failure between the Body Control Module (BCM) and other modules in the vehicle's network, suggesting a problem with data exchange or connectivity

Definition

The OBD2 code U1905 indicates a communication failure between the Body Control Module (BCM) and other modules in the vehicle's network, suggesting a problem with data exchange or connectivity

Common causes

  • Faulty Body Control Module (BCM)
  • Damaged wiring or connectors
  • Poor ground connections
  • Corroded terminals
  • Communication network issues (CAN bus problems)
  • Software glitches or programming errors
  • Malfunctioning related modules (e.g., PCM, ABS)
  • Low battery voltage or power supply issues

Common misdiagnoses

  • Faulty Body Control Module (BCM)
  • Wiring issues or shorts in the communication lines
  • Defective or corroded connectors
  • Malfunctioning other control modules (e.g., PCM, ABS)
  • Battery or power supply issues
  • Software or firmware glitches
  • Grounding problems
  • Intermittent faults in the 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 related issues

  2. 2.Inspect Wiring and Connectors

  3. 3.Visually inspect the wiring and connectors associated with the BCM and other modules. 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 BCM is receiving the correct voltage. Use a multimeter to check the power supply to the BCM

  7. 7.Verify that the fuses related to the BCM and communication circuits are intact

  8. 8.Test the BCM

  9. 9.If possible, perform a self-test of the BCM using a scan tool. Some scan tools can communicate with the BCM to check for internal faults

  10. 10.If the BCM is not responding, it may need to be replaced

  11. 11.Inspect Other Modules

  12. 12.Check the other modules that communicate with the BCM (e.g., ABS, PCM, etc.) for faults. A malfunctioning module can disrupt communication

  13. 13.Ensure that all modules are properly connected and functioning

  14. 14.Check for Software Updates

  15. 15.Some vehicles may require software updates for the BCM or other modules. Check with the manufacturer or a dealership for any available updates

  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 and take the vehicle for a test drive to see if the code returns

  18. 18.Consult Technical Service Bulletins (TSBs)

  19. 19.Look for any TSBs related to the U1905 code for your specific vehicle make and model. Manufacturers may have specific recommendations or known issues

  20. 20.Professional Diagnosis

  21. 21.If the issue persists after performing the above steps, consider seeking help from a professional mechanic or dealership. They may have specialized tools and knowledge to diagnose complex communication issues. By following these steps, you can systematically identify and resolve the underlying cause of the U1905 code