U1645 – Body Control Module Communication Failure

The ODBII code U1645: Body Control Module Communication Failure indicates a loss of communication between the Body Control Module (BCM) and other control modules in the vehicle, which may affect various electrical systems and functions.

The severity of ODBII code **U1645: Body Control Module Communication Failure** is generally considered moderate to severe.

Common Causes For: U1585: BCM Communication Failure

• Faulty Body Control Module (BCM)
• Damaged wiring or connectors
• Poor ground connections
• Communication network issues (CAN bus problems)
• Faulty or disconnected sensors
• Software or firmware issues in the BCM
• Corrosion in connectors or terminals
• Low battery voltage or power supply issues

Common misdiagnosis for U1645: Body Control Module Communication Failure

• Faulty Body Control Module (BCM)
• Wiring issues or shorts in the communication lines
• Faulty or corroded connectors
• Malfunctioning other control modules
• Power supply issues to the BCM
• Software or firmware issues in the BCM
• Faulty sensors or actuators related to the BCM
• Grounding issues in the vehicle’s electrical system

Common Troubleshooting Steps

The OBD-II code **U1645: Body Control Module Communication Failure** indicates that there is a communication issue between the Body Control Module (BCM) and other modules in the vehicle’s network. Here are some common troubleshooting steps to diagnose and resolve this issue:

• Check for Other Codes:
• Use an OBD-II scanner to check for any additional trouble codes. Other codes may provide more context or indicate related issues.
• Inspect Wiring and Connectors:
• Visually inspect the wiring and connectors associated with the BCM and other modules. Look for signs of damage, corrosion, loose connections, or broken wires.
• Pay special attention to the ground connections, as poor grounding can lead to communication issues.
• Check for Power Supply:
• Ensure that the BCM is receiving the proper voltage. Use a multimeter to check the power supply to the BCM and verify that it is within the manufacturer’s specifications.
• Test the Body Control Module:
• If the wiring and power supply are good, the BCM itself may be faulty. You can test the BCM by checking its functionality with a scan tool or by replacing it with a known good unit.
• Inspect the CAN Bus:
• The BCM communicates with other modules via the Controller Area Network (CAN) bus. Check for any issues with the CAN bus wiring, such as shorts or opens.
• Use a scan tool to monitor the CAN bus for proper communication between modules.
• Check for Software Updates:
• Sometimes, communication issues can be resolved with a software update. Check with the vehicle manufacturer for any available updates for the BCM or other related modules.
• Clear Codes and Test Drive:
• After performing the above checks and repairs, clear the trouble codes using the OBD-II scanner and take the vehicle for a test drive to see if the code returns.
• Consult Service Manual:
• Refer to the vehicle’s service manual for specific diagnostic procedures and wiring diagrams related to the BCM and communication network.
• Professional Diagnosis:
• If the issue persists after performing these steps, consider seeking help from a professional mechanic or dealership with experience in diagnosing BCM communication issues. By following these steps, you should be able to identify and resolve the cause of the U1645 code.