WOMS
U code network High severity

U1039 Lost Communication with Body Control Module (BCM)"

The OBD2 code U1039 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 functions and systems in the vehicle

Definition

The OBD2 code U1039 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 functions and systems in the vehicle

Common causes

  • Faulty Body Control Module (BCM)
  • Damaged wiring or connectors
  • Poor ground connection
  • Corroded terminals
  • Faulty communication network (CAN bus issues)
  • Blown fuses
  • Software or firmware issues in the BCM
  • Intermittent electrical connections
  • Other module failures affecting communication

Common misdiagnoses

  • Faulty Body Control Module (BCM)
  • Wiring issues or shorts in the communication lines
  • Faulty or corroded connectors
  • Issues with the power supply to the BCM
  • Problems with other control modules
  • Software or firmware issues in the BCM
  • Faulty ignition switch
  • Battery or charging system problems
  • Grounding issues
  • Faulty sensors or actuators related to the BCM

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, corroded, or damaged

  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. Test Communication Lines

    CAN Bus: Use a scan tool to check the communication on the CAN bus. If other modules are not communicating, there may be a fault in the bus itself

  9. 9. Scope Testing

    If available, use an oscilloscope to check for proper signal patterns on the communication lines

  10. 10. Check for Intermittent Issues

    Temperature and Vibration: Sometimes, issues can be intermittent. Check if the problem occurs under specific conditions, such as temperature changes or vibrations

  11. 11. Inspect Related Modules

    Other Control Modules: Check if other control modules are functioning properly. A fault in another module can sometimes affect communication with the BCM

  12. 12. Perform a Hard Reset

    Disconnect the vehicle's battery for a few minutes to reset the BCM and other modules. Reconnect and see if the code reappears

  13. 13. Consult Technical Service Bulletins (TSBs)

    Check for any TSBs related to the BCM or communication issues for your specific vehicle make and model. Manufacturers may have known fixes or updates

  14. 14. Replace the BCM (if necessary)

    If all other troubleshooting steps fail and the BCM is determined to be faulty, consider replacing it. Ensure proper programming and configuration after replacement.1

  15. 15. Seek Professional Help

    If you are unable to resolve the issue, it may be best to consult a professional mechanic or dealership with experience in diagnosing and repairing BCM-related issues.Conclusion Always remember to take safety precautions when working on a vehicle's electrical system. If you're not comfortable performing these steps, it's advisable to seek professional assistance