WOMS
U code network High severity

U1390 Lost Communication with the Body Control Module (BCM)

The OBD2 code U1390 indicates that there is a loss of communication between the vehicle's control module and the Body Control Module (BCM), which may affect various electrical systems and functions

Definition

The OBD2 code U1390 indicates that there is a loss of communication between the vehicle's control module and the Body Control Module (BCM), which may affect various electrical systems and functions

Common causes

  • Faulty Body Control Module (BCM)
  • Damaged wiring or connectors
  • Corroded terminals
  • Blown fuses
  • Poor ground connections
  • Software issues or programming errors
  • Intermittent electrical connections
  • Faulty communication network (CAN bus issues)

Common misdiagnoses

  • Faulty Body Control Module (BCM)
  • Wiring issues or shorts in the communication lines
  • Faulty or corroded connectors
  • Issues with the Powertrain Control Module (PCM)
  • Malfunctioning sensors or actuators
  • Battery or charging system problems
  • Faulty ignition switch
  • Software or firmware issues in the BCM or other modules

Troubleshooting steps

  1. 1. Check for Other Codes

    Use an OBD-II scanner to check for any additional trouble codes. Sometimes, other codes can provide context or indicate related issues

  2. 2. Inspect the Wiring and Connectors

    Visual Inspection: Check the wiring harness and connectors related to the BCM for any signs of damage, corrosion, or loose connections

  3. 3. Connector Pins

    Ensure that the pins in the connectors are not bent or corroded

  4. 4. Check Power and Ground

    Power Supply: Verify that the BCM is receiving the correct voltage. Use a multimeter to check the power supply to the BCM

  5. 5. Ground Connections

    Ensure that the ground connections for the BCM are secure and free of corrosion

  6. 6. Inspect the BCM

    Physical Condition: Check the BCM for any signs of physical damage or water intrusion

  7. 7. Reprogramming

    If the BCM has been replaced, ensure that it has been properly programmed to the vehicle

  8. 8. Check for Communication Issues

    CAN Bus: Inspect the CAN bus wiring for shorts, opens, or other issues. The BCM communicates with other modules via the CAN bus, so any issues here can lead to communication loss

  9. 9. Scan Other Modules

    Use a scan tool to check if other modules can communicate with the BCM. If they cannot, the issue may be with the CAN bus or the BCM itself

  10. 10. Test the BCM

    If possible, test the BCM in another vehicle (if you have access to one) to determine if the module itself is faulty

  11. 11. Alternatively, you can try replacing the BCM with a known good unit

  12. 12. Check for Software Updates

    Check if there are any software updates available for the BCM or the vehicle’s control modules. Sometimes, manufacturers release updates to fix communication issues

  13. 13. Clear Codes and Test Drive

    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

  14. 14. Consult Technical Service Bulletins (TSBs)

    Look for any TSBs related to the specific make and model of the vehicle. Manufacturers may have issued bulletins regarding known issues with the BCM or communication problems

  15. 15. Seek Professional Help

    If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or an automotive electrician who has experience with BCM issues. By following these steps, you should be able to identify and resolve the cause of the U1390 code. Always ensure safety and proper procedures when working on vehicle electronics