WOMS
U code network High severity

U1909 U1909: "BCM Communication Failure

The OBD2 code U1909 indicates a communication failure between the Body Control Module (BCM) and other modules in the vehicle's network, suggesting a problem with data exchange or connectivity

Definition

The OBD2 code U1909 indicates a communication failure between the Body Control Module (BCM) and other modules in the vehicle's network, suggesting a problem with data exchange or connectivity

Common causes

  • Faulty Body Control Module (BCM)
  • Damaged wiring or connectors
  • Poor ground connections
  • Corroded terminals
  • Software issues or programming errors
  • Malfunctioning CAN bus
  • Interference from aftermarket accessories
  • Low battery voltage or weak battery
  • Faulty or damaged sensors connected to the BCM

Common misdiagnoses

  • Faulty Body Control Module (BCM)
  • Wiring issues or shorts in the communication lines
  • Defective or corroded connectors
  • Malfunctioning other control modules (e.g., PCM, ECM)
  • Battery or power supply issues
  • Software or firmware glitches
  • Grounding 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. Other codes can provide context and help identify the root cause of the communication failure

  2. 2. Inspect Wiring and Connectors

    Visually inspect the wiring and connectors related to the BCM. Look for signs of damage, corrosion, or loose connections. Pay special attention to the ground connections, as poor grounding can lead to communication issues

  3. 3. Check Power Supply

    Ensure that the BCM is receiving the correct voltage. Use a multimeter to check the power supply to the BCM. If the voltage is low or absent, trace the wiring back to the power source

  4. 4. Test the BCM

    If possible, test the BCM to ensure it is functioning correctly. This may involve using specialized diagnostic equipment or swapping the BCM with a known good unit

  5. 5. Inspect Other Modules

    Since the BCM communicates with other modules, check those modules for faults. Look for any signs of failure or communication issues in related systems (e.g., ABS, airbag, etc.)

  6. 6. Check for Short Circuits

    Use a multimeter to check for short circuits in the wiring harness connected to the BCM. A short circuit can disrupt communication between modules

  7. 7. Perform a Network Test

    If you have access to a scan tool that can perform network tests, use it to check the communication between the BCM and other modules. This can help identify which module is causing the communication failure

  8. 8. Update Software/Firmware

    Check if there are any software or firmware updates available for the BCM or other related modules. Sometimes, communication issues can be resolved with an update

  9. 9. Clear Codes and Test Drive

    After performing any repairs or adjustments, clear the trouble codes and take the vehicle for a test drive to see if the U1909 code returns

  10. 10. Seek Professional Help

    If the issue persists after performing the above steps, consider seeking help from a professional mechanic or automotive technician who has experience with BCM-related issues. By following these troubleshooting steps, you should be able to identify and resolve the cause of the U1909 code