WOMS
U code network High severity

U1694 Lost Communication with Body Control Module (BCM)"

The OBD2 code U1694 indicates that there is a communication failure 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 U1694 indicates that there is a communication failure 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 power supply to the BCM
  • Malfunctioning other control modules
  • Software or firmware issues in the BCM
  • Battery or charging system problems
  • Grounding issues in the vehicle's 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 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 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 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: If your vehicle uses a CAN bus system, check the communication lines for continuity and proper voltage levels

  9. 9. Scan Tool

    Use a scan tool to see if you can communicate with the BCM. If you cannot, it may indicate a problem with the BCM itself or the communication lines

  10. 10. Check for Intermittent Issues

    Temperature Sensitivity: Sometimes, issues can be temperature-related. Check if the problem occurs only under certain conditions (e.g., after the vehicle has been running for a while)

  11. 11. Vibration

    Check if the issue occurs when the vehicle is in motion or over bumps

  12. 12. Look for Related Modules

    If other modules are also having communication issues, it may indicate a broader problem with the vehicle’s network. Check for issues with other control modules that communicate with the BCM

  13. 13. Perform a Hard Reset

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

  14. 14. 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 issued fixes for known problems

  15. 15. 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

  16. 16. 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. By following these steps, you should be able to identify the cause of the U1694 code and take appropriate action to resolve it