WOMS
U code network High severity

U1320 Lost Communication with the Body Control Module (BCM)

The OBD2 code U1320 indicates 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 U1320 indicates 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
  • Malfunctioning sensors or components connected to the BCM

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
  • Battery or charging system problems
  • Faulty fuses related to the BCM
  • Software or programming issues in the BCM
  • Grounding issues in the electrical system
  • Other communication network failures (e.g., CAN bus issues)

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 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, it may need to be reprogrammed 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 or a specialized scan tool to monitor the data lines

  9. 9. Network Issues

    Look for any other modules on the network that may be causing communication issues

  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

    Ensure that the BCM is securely mounted and not subject to excessive vibration

  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. Scan Tool Functions

    Use a professional scan tool to attempt to communicate with the BCM. If communication is not possible, it may indicate a fault in the BCM itself or the wiring

  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 known fixes for common problems

  15. 15. Replace the BCM (if necessary)

    If all other troubleshooting steps fail and the BCM is determined to be faulty, replacement may be necessary. Ensure proper programming and configuration after replacement.Conclusion Always follow safety precautions when working on a vehicle's electrical system. If you're not comfortable performing these steps, or if the issue persists after your troubleshooting, it may be best to consult a professional mechanic or technician for further diagnosis and repair