WOMS
C code chassis High severity

C0291 Lost Communications With BCM

The OBD2 code C0291 indicates that there is a loss of communication between the vehicle's control module and the Body Control Module (BCM), which can affect various electrical systems and functions

Definition

The OBD2 code C0291 indicates that there is a loss of communication between the vehicle's control module and the Body Control Module (BCM), which can affect various electrical systems and functions

Common causes

  • Faulty Body Control Module (BCM)
  • Wiring issues (damaged, corroded, or loose connections)
  • Faulty connectors or terminals
  • Software issues or programming errors
  • Power supply problems to the BCM
  • Malfunctioning fuses
  • Interference from aftermarket accessories or modifications
  • Grounding 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
  • Faulty Instrument Cluster
  • Malfunctioning Engine Control Module (ECM)
  • Problems with the CAN bus system
  • Software or firmware issues in the BCM
  • Battery or charging system problems
  • Faulty sensors or actuators related to the BCM

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 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. Test the BCM

    Power and Ground: Verify that the BCM is receiving proper power and ground. Use a multimeter to check voltage at the BCM connector

  5. 5. Communication Lines

    Check the communication lines (CAN bus) for continuity and proper voltage levels

  6. 6. Check Fuses

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

  7. 7. Scan for BCM Issues

    Use a professional-grade scan tool to access the BCM and check for any internal faults or issues. Some scan tools can perform BCM-specific tests

  8. 8. Reset the BCM

    Sometimes, resetting the BCM can resolve communication issues. This can be done by disconnecting the battery for a few minutes or using a scan tool to clear codes

  9. 9. Inspect for Interference

    Check for any aftermarket devices or modifications that may interfere with the BCM's operation, such as alarm systems or remote start systems

  10. 10. Check for Software Updates

    Verify if there are any software updates available for the BCM or ECM. Sometimes, manufacturers release updates to fix communication issues

  11. 11. Replace the BCM

    If all other steps fail and the BCM is determined to be faulty, consider replacing it. Ensure that the replacement BCM is compatible with your vehicle and properly programmed

  12. 12. Professional Diagnosis

    If you are unable to resolve the issue, it may be best to consult a professional mechanic or dealership for a more in-depth diagnosis.Conclusion Always remember to take safety precautions when working on a vehicle's electrical system. If you're not comfortable performing these steps, it's advisable to seek help from a qualified technician