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U code network High severity

U1966 Lost Communication with the Body Control Module (BCM)

The OBD2 code U1966 indicates that there is a communication failure between the vehicle's control module and the Body Control Module (BCM), which may affect various electrical systems and functions

Definition

The OBD2 code U1966 indicates that there is a communication failure 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
  • Faulty communication network (CAN bus issues)
  • Software or firmware issues
  • Grounding problems
  • 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
  • Battery or charging system problems
  • Faulty fuses related to the BCM
  • Software or programming issues in 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 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 Fuses

    Check the vehicle’s fuse box for any blown fuses that may affect the BCM or related systems. Replace any blown fuses and retest

  7. 7. Test the BCM

    If possible, perform a functional test of the BCM. This may require specialized diagnostic equipment or software

  8. 8. If you have access to a known good BCM, you can swap it out temporarily to see if the issue resolves

  9. 9. Check for Communication Issues

    Use a scan tool to check if the BCM is communicating with other modules in the vehicle. If other modules are also not communicating, the issue may be with the communication bus (CAN bus)

  10. 10. Inspect the CAN bus wiring for damage or shorts

  11. 11. Look for Environmental Factors

    Check for moisture or water intrusion in the BCM area, which can cause communication issues

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

  13. 13. Software Updates

    Check if there are any software updates available for the BCM. Sometimes, manufacturers release updates to fix known issues

  14. 14. Reset the System

    After performing the above checks, clear the trouble codes using the OBD-II scanner and see if the code returns after a test drive

  15. 15. Consult Technical Service Bulletins (TSBs)

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

  16. 16. Professional Diagnosis

    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 access to advanced diagnostic tools and resources. By following these steps, you can systematically identify and address the underlying cause of the U1966 code