U1318 – Lost Communication with Body Control Module (BCM).

The ODBII code U1318 indicates that there is a communication failure between the vehicle’s Body Control Module (BCM) and other modules, which may affect various electrical functions and systems in the vehicle.

The severity of ODBII code U1318 is generally considered moderate to severe, as it indicates a communication issue that can affect multiple vehicle systems.

Common Causes For: U1317 CAN Communication Bus Off.

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

Common misdiagnosis for U1318 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
• Malfunctioning other control modules
• Software or firmware issues in the BCM
• Battery or charging system problems
• Faulty ignition switch
• Grounding issues in the electrical system
• Intermittent communication faults due to environmental factors

Common Troubleshooting Steps

When dealing with the OBD-II code U1318, 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. Sometimes, multiple codes can provide more context for the issue.
• Inspect 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 or corroded.
• 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.
• Test the BCM: If possible, test the BCM itself. This may involve using a scan tool to communicate with the BCM and check for any internal faults.
• If you have access to a known good BCM, you can swap it out to see if the issue persists.
• Inspect Related Modules: Check for communication issues with other modules in the vehicle. The BCM often communicates with other control modules, and a fault in one of these can cause communication issues.
• Use a scan tool to check if other modules are reporting communication errors.
• Check for Short Circuits: Inspect the wiring for any short circuits that may be affecting communication. This can include checking for shorts to ground or power.
• Look for Software Issues: Ensure that the vehicle’s software is up to date. Sometimes, a software update can resolve communication issues.
• If the BCM has been recently programmed or updated, ensure that the process was completed successfully.
• 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 reappears.
• Check for Environmental Factors: Ensure that there are no environmental factors affecting the BCM, such as water intrusion or excessive heat.
• Consult Technical Service Bulletins (TSBs): Check for any TSBs related to the specific make and model of the vehicle. Manufacturers may have issued guidance on common issues related to the BCM.1
• Seek Professional Help: If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or technician who has experience with the specific vehicle and its systems. By following these troubleshooting steps, you can systematically identify and address the cause of the U1318 code.