U1966 – Lost Communication with the Body Control Module (BCM).

The ODBII code U1966 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 U1966 is generally considered moderate to severe.

Common Causes For: U1965 Data Bus Communication Failure.

• Faulty Body Control Module (BCM)
• Damaged wiring or connectors
• Corroded terminals
• Blown fuses
• Faulty communication network (CAN bus issues)
• Software or firmware issues
• Grounding problems
• Intermittent electrical connections

Common misdiagnosis for U1966 Lost Communication with the Body Control Module (BCM).

• Faulty Body Control Module (BCM)
• Wiring issues or shorts in the communication lines
• Faulty or corroded connectors
• Issues with the Powertrain Control Module (PCM)
• Malfunctioning Instrument Cluster
• Battery or charging system problems
• Faulty fuses related to the BCM
• Software or programming issues in the BCM

Common Troubleshooting Steps

When dealing with OBD-II code U1966, which indicates “Lost Communication with the 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 Other Codes: Use an OBD-II scanner to check for any additional trouble codes. Sometimes, other codes can provide context or indicate related issues.
• Inspect the Wiring and Connectors: **Visual Inspection: Check the wiring harness and connectors leading 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 damaged.
• Check Power and Ground: **Power Supply: Verify that the BCM is receiving the correct voltage. Use a multimeter to check the power supply at the BCM connector.
• **Ground Connections: Ensure that the ground connections for the BCM are secure and free of corrosion.
• Inspect Fuses: Check the vehicle’s fuse box for any blown fuses that may affect the BCM or related systems. Replace any blown fuses and retest.
• Test the BCM: If possible, perform a functional test of the BCM. This may require specialized diagnostic equipment or software.
• If you have access to a known good BCM, you can swap it out temporarily to see if the issue resolves.
• Check for Communication Issues: Use a scan tool to check if the BCM is communicating with other modules in the vehicle. If other modules are also not communicating, the issue may be with the communication bus (CAN bus).
• Inspect the CAN bus wiring for damage or shorts.
• Look for Environmental Factors: Check for moisture or water intrusion in the BCM area, which can cause communication issues.
• Ensure that the BCM is mounted securely and not subject to excessive vibration.
• Software Updates: Check if there are any software updates available for the BCM. Sometimes, manufacturers release updates to fix known issues.
• Reset the System: After performing the above checks, clear the trouble codes using the OBD-II scanner and see if the code returns after a test drive.
• Consult Technical Service Bulletins (TSBs): Look for any TSBs related to the specific make and model of your vehicle. Manufacturers may have issued guidance on common issues related to the BCM.1
• Professional Diagnosis: If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or dealership for further diagnosis. They may have access to advanced diagnostic tools and resources. By following these steps, you can systematically identify and address the underlying cause of the U1966 code.