U1540 – BCM Communication Failure

The ODBII code U1540 indicates a communication failure between the Body Control Module (BCM) and other modules in the vehicle’s network, which can affect various electrical functions and systems.

The severity of ODBII code U1540: “BCM Communication Failure” is generally considered moderate to severe.

Common Causes For: U1539 U1539: “Module Communication Failure”

• Faulty Body Control Module (BCM)
• Poor electrical connections or wiring issues
• Corroded or damaged connectors
• Malfunctioning sensors or components connected to the BCM
• Software or firmware issues in the BCM
• Low battery voltage or power supply issues
• Interference from aftermarket accessories or modifications

Common misdiagnosis for U1540 U1540: “BCM Communication Failure”

• Faulty Body Control Module (BCM)
• Wiring issues or shorts in the communication lines
• Defective or corroded connectors
• Malfunctioning Instrument Cluster
• Issues with the Powertrain Control Module (PCM)
• Problems with the Anti-lock Braking System (ABS) module
• Battery or charging system problems
• Software glitches or programming errors 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 U1540 indicates a “BCM Communication Failure,” which typically means there is a problem with the communication between the Body Control Module (BCM) and other modules in the vehicle. Here are some common troubleshooting steps to diagnose and resolve this issue:

• 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: Visually inspect the wiring and connectors related to the BCM. Look for signs of damage, corrosion, or loose connections.
• Pay special attention to the ground connections, as poor grounding can lead to communication issues.
• Check the BCM: Ensure that the BCM is properly secured and that there are no signs of physical damage.
• If possible, test the BCM with a known good unit to see if the problem persists.
• Inspect Other Modules: Check the other modules that communicate with the BCM (e.g., PCM, ABS, airbag module). Ensure they are functioning correctly and that their connections are secure.
• Test Communication Lines: Use a multimeter or an oscilloscope to test the communication lines (CAN bus) for continuity and proper voltage levels.
• Look for short circuits or open circuits in the communication lines.
• Check for Software Updates: Verify if there are any software updates available for the BCM or other related modules. Sometimes, manufacturers release updates to fix communication issues.
• Perform a Hard Reset: Disconnect the vehicle’s battery for a few minutes to reset the BCM and other modules. Reconnect the battery and see if the code reappears.
• Inspect Fuses: Check the fuses related to the BCM and other modules. A blown fuse can interrupt communication.
• Scan for Communication Issues: Use a professional-grade scan tool to perform a network scan. This can help identify which module is not communicating properly.
• Consult Technical Service Bulletins (TSBs): Look for any TSBs related to the U1540 code for your specific vehicle make and model. Manufacturers may have specific fixes or recommendations.1
• Seek Professional Help: If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or dealership for further diagnosis. By following these troubleshooting steps, you can systematically identify and resolve the underlying cause of the U1540 code.