U1665 – Lost Communication with Body Control Module (BCM).

The ODBII code U1665 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.

The severity of ODBII code U1665 is generally considered moderate to high.

Common Causes For: U1664 U1664: “Communication Network Malfunction”

• Faulty Body Control Module (BCM)
• Damaged wiring or connectors
• Poor ground connection
• Corroded terminals
• Faulty communication network (CAN bus)
• Software issues or programming errors
• Blown fuses related to the BCM
• Intermittent electrical issues
• Other module failures affecting communication

Common misdiagnosis for U1665 Lost Communication with Body Control Module (BCM)”.

• 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
• Problems with other control modules
• Software or firmware issues in the BCM
• Faulty ignition switch
• Battery or charging system problems

Common Troubleshooting Steps

When dealing with the OBD-II code U1665, which indicates “Lost Communication with Body Control Module (BCM),” there are several common troubleshooting steps you can follow to diagnose and potentially resolve the issue. Here’s a structured approach:

• 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.
• Inspect the Wiring and Connectors: **Visual Inspection: Check the wiring harness and connectors related to the BCM for any signs of damage, corrosion, or loose connections.
• **Connector Pins: Ensure that the pins in the connectors are not bent, corroded, or pushed back.
• Check Power and Ground: **Power Supply: Verify that the BCM is receiving the correct voltage. Use a multimeter to check the power supply to the BCM.
• **Ground Connections: Ensure that the ground connections for the BCM are secure and free of corrosion.
• Inspect the BCM: **Physical Condition: Check the BCM for any signs of physical damage or water intrusion.
• **Reprogramming: If the BCM has been replaced, ensure that it has been properly programmed to the vehicle.
• Test Communication Lines: **CAN Bus Communication: Use a scan tool to check the communication on the CAN bus. If other modules are not communicating, there may be a fault in the bus itself.
• **Scope Testing: If available, use an oscilloscope to check for proper signal patterns on the communication lines.
• Check for Short Circuits: Inspect the wiring for any short circuits to ground or power that could affect communication with the BCM.
• Look for Environmental Factors: Check for any environmental factors that could affect the BCM, such as moisture or extreme temperatures.
• Perform a Hard Reset: Disconnect the vehicle’s battery for a few minutes to reset the BCM and other modules. Reconnect and see if the code returns.
• Consult Technical Service Bulletins (TSBs): Look for any TSBs related to the specific make and model of the vehicle that may address known issues with the BCM or communication problems.
• Replace the BCM (if necessary): If all other troubleshooting steps fail and the BCM is determined to be faulty, consider replacing it. Ensure proper programming and configuration after replacement.1
• Seek Professional Help: If you are unable to resolve the issue, it may be best to consult a professional mechanic or dealership with experience in diagnosing and repairing BCM-related issues.Conclusion By following these steps, you can systematically diagnose the cause of the U1665 code. Always ensure safety precautions are taken when working with vehicle electronics, and consult the vehicle’s service manual for specific procedures related to your make and model.