WOMS
U code network High severity

U1636 U1636: "BCM Communication Failure

The OBD2 code U1636 indicates a communication failure between the Body Control Module (BCM) and other modules in the vehicle's network

Definition

The OBD2 code U1636 indicates a communication failure between the Body Control Module (BCM) and other modules in the vehicle's network

Common causes

  • Faulty Body Control Module (BCM)
  • Poor electrical connections or wiring issues
  • Corroded or damaged connectors
  • Malfunctioning sensors or actuators
  • Software or firmware issues in the BCM
  • Low battery voltage or power supply issues
  • Interference from aftermarket accessories
  • Faulty communication lines (CAN bus issues)

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)
  • Power supply issues to the BCM
  • Software or firmware issues in the BCM
  • Grounding problems
  • Faulty sensors or actuators related to the BCM
  • Intermittent communication issues due to environmental factors
  • Battery or charging system problems

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 additional context for the issue

  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

  3. 3. Pay special attention to the ground connections, as poor grounding can lead to communication issues

  4. 4. Check Power Supply

    Ensure that the BCM is receiving the correct voltage. Use a multimeter to check the power supply to the BCM

  5. 5. Verify that the fuses related to the BCM and communication circuits are intact

  6. 6. Test the BCM

    If possible, perform a functional test of the BCM using a scan tool. Check for any abnormal readings or failures

  7. 7. If the BCM is suspected to be faulty, consider replacing it or reprogramming it if necessary

  8. 8. Inspect Other Modules

    Check the communication between the BCM and other modules (e.g., ECM, ABS, etc.). If other modules are malfunctioning, they may affect the BCM's ability to communicate

  9. 9. Look for any signs of failure in other modules that could be causing the communication issue

  10. 10. Check for Short Circuits

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

  11. 11. Perform a Network Test

    If your scan tool supports it, perform a network test to check for communication between all modules on the vehicle's network

  12. 12. Look for any modules that are not responding or are showing communication errors

  13. 13. Clear Codes and Test Drive

    After performing the above checks and repairs, clear the trouble codes using the OBD-II scanner

  14. 14. Take the vehicle for a test drive to see if the code reappears

  15. 15. Consult Technical Service Bulletins (TSBs)

    Check for any TSBs related to the U1636 code for your specific vehicle make and model. Manufacturers may have specific fixes or updates for known issues

  16. 16. Seek Professional Help

    If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or dealership for further diagnosis and repair. By following these troubleshooting steps, you can systematically identify and resolve the underlying cause of the U1636 code