U1855 – Lost Communication with Body Control Module (BCM).

The ODBII code U1855 indicates that there is a communication failure between the vehicle’s control modules, specifically indicating a lost connection with the Body Control Module (BCM).

The severity of ODBII code U1855 is generally considered moderate to severe.

Common Causes For: U1854 U1854: “Module Communication Failure”

• Faulty Body Control Module (BCM)
• Damaged wiring or connectors
• Corroded terminals
• Poor ground connection
• Faulty communication network (CAN bus issues)
• Blown fuses
• Software or firmware issues in the BCM
• Intermittent electrical connections

Common misdiagnosis for U1855 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 modules in the network
• Software or firmware issues in the BCM
• Battery or charging system problems
• Grounding issues in the vehicle’s electrical system

Common Troubleshooting Steps

When dealing with the OBD-II code U1855, 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 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 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.
• Check for Communication Issues: **CAN Bus Communication: Use a scan tool to check if other modules in the vehicle are communicating properly. If other modules are also not communicating, there may be a problem with the CAN bus.
• **Network Integrity: Inspect the CAN bus wiring for shorts, opens, or other issues.
• Test the BCM: If possible, test the BCM in another vehicle of the same make and model to determine if the module is faulty.
• Alternatively, you can use a known good BCM to see if the issue resolves.
• Check for Software Updates: Check if there are any software updates available for the BCM or other related modules. Sometimes, manufacturers release updates to fix communication issues.
• Clear Codes and Test Drive: After performing the above checks and repairs, clear the codes using the OBD-II scanner and take the vehicle for a test drive to see if the code returns.
• Consult Technical Service Bulletins (TSBs): Look for any TSBs related to the U1855 code for your specific vehicle make and model. Manufacturers may have specific recommendations or known issues.
• Seek Professional Help: If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or an automotive technician with experience in electrical systems and BCM diagnostics. By following these steps, you should be able to identify the root cause of the U1855 code and take appropriate action to resolve the communication issue with the Body Control Module.