WOMS
U code network High severity

U1641 Lost Communication with Body Control Module (BCM)

The OBD2 code U1641 indicates 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 U1641 indicates 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 connections
  • Corroded terminals
  • Faulty communication network (CAN bus issues)
  • Blown fuses
  • Software or firmware issues in the BCM
  • Intermittent electrical connections

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 Instrument Cluster
  • Problems with the CAN bus system
  • Low battery voltage or power supply issues
  • Faulty sensors or actuators related to the BCM
  • Software or firmware issues in the BCM
  • Grounding issues in the electrical system

Troubleshooting steps

  1. 1. Check for Additional Codes

    Use an OBD-II scanner to check for any other trouble codes that may be present. This can provide more context and help identify related issues

  2. 2. Inspect the Wiring and Connectors

    Visual Inspection: Check the wiring harness and connectors leading 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 pushed back

  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 at the BCM connector

  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, such as cracks or burn marks

  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: If your vehicle uses a CAN bus system, check the communication lines for continuity and proper signal. You may need an oscilloscope to check for data transmission

  9. 9. Other Modules

    Check if other modules in the vehicle are communicating properly. If they are also having communication issues, it may indicate a broader network problem

  10. 10. Check for Short Circuits

    Use a multimeter to check for short circuits in the wiring harness that could affect communication with the BCM

  11. 11. Inspect Fuses

    Check the fuses related to the BCM and other modules. A blown fuse can interrupt communication

  12. 12. Perform a Hard Reset

    Disconnect the battery for a few minutes to reset the vehicle’s electronic systems. Reconnect and see if the code reappears

  13. 13. Scan for Updates

    Check if there are any software updates available for the BCM or other related modules. Sometimes, manufacturers release updates to fix communication issues

  14. 14. Consult Technical Service Bulletins (TSBs)

    Look for any TSBs related to the U1641 code for your specific vehicle make and model. Manufacturers may have documented common issues and fixes.1

  15. 15. Seek Professional Help

    If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or dealership for further diagnosis. They may have specialized tools and knowledge to address complex issues. By following these steps, you should be able to identify the root cause of the U1641 code and take appropriate action to resolve it