WOMS
U code network High severity

U1318 Lost Communication with Body Control Module (BCM)"

The OBD2 code U1318 indicates that there is a communication failure between the vehicle's Body Control Module (BCM) and other modules, which may affect various electrical functions and systems in the vehicle

Definition

The OBD2 code U1318 indicates that there is a communication failure between the vehicle's Body Control Module (BCM) and other modules, 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)
  • Software issues or programming errors
  • Blown fuses related to the BCM
  • Intermittent electrical issues

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
  • Faulty ignition switch
  • Grounding issues in the electrical system
  • Intermittent communication faults due to environmental factors

Troubleshooting steps

  1. 1. Check for Additional Codes

    Use an OBD-II scanner to check for any other trouble codes that may be present. Sometimes, multiple codes can provide more context for the issue

  2. 2. Inspect 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. Test the BCM

    If possible, test the BCM itself. This may involve using a scan tool to communicate with the BCM and check for any internal faults

  7. 7. If you have access to a known good BCM, you can swap it out to see if the issue persists

  8. 8. Inspect Related Modules

    Check for communication issues with other modules in the vehicle. The BCM often communicates with other control modules, and a fault in one of these can cause communication issues

  9. 9. Use a scan tool to check if other modules are reporting communication errors

  10. 10. Check for Short Circuits

    Inspect the wiring for any short circuits that may be affecting communication. This can include checking for shorts to ground or power

  11. 11. Look for Software Issues

    Ensure that the vehicle’s software is up to date. Sometimes, a software update can resolve communication issues

  12. 12. If the BCM has been recently programmed or updated, ensure that the process was completed successfully

  13. 13. 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

  14. 14. Check for Environmental Factors

    Ensure that there are no environmental factors affecting the BCM, such as water intrusion or excessive heat

  15. 15. Consult Technical Service Bulletins (TSBs)

    Check for any TSBs related to the specific make and model of the vehicle. Manufacturers may have issued guidance on common issues related to the BCM.1

  16. 16. Seek Professional Help

    If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or technician who has experience with the specific vehicle and its systems. By following these troubleshooting steps, you can systematically identify and address the cause of the U1318 code