U1520 – Body Control Module Communication Error

The ODBII code U1520 indicates a communication error between the Body Control Module (BCM) and other modules in the vehicle, suggesting a potential issue with wiring, connectors, or the BCM itself.

Moderate.

Common Causes For: U1519 U1519: Transmission Control Module Communication Error

• Faulty Body Control Module (BCM)
• Poor electrical connections or wiring issues
• Corroded connectors
• Faulty or damaged CAN bus wiring
• Malfunctioning or incompatible modules
• Software or firmware issues
• Low battery voltage or power supply problems
• Interference from aftermarket accessories or modifications

Common misdiagnosis for U1520 U1520: Body Control Module Communication Error

• Faulty Body Control Module (BCM)
• Wiring issues or short circuits
• Corrupted software or firmware in the BCM
• Faulty connectors or terminals
• Issues with other control modules (e.g., Engine Control Module)
• Battery or charging system problems
• Grounding issues
• Faulty sensors related to the BCM
• Communication network issues (e.g., CAN bus problems)

Common Troubleshooting Steps

The OBD-II code U1520 indicates a communication error 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 Other Codes: Use an OBD-II scanner to check for any additional trouble codes. Sometimes, related codes can provide more context for the issue.
• Inspect Wiring and Connectors:
• Visually inspect the wiring and connectors associated with the BCM and other modules for any signs of damage, corrosion, or loose connections.
• Pay special attention to the ground connections, as poor grounding can lead to communication issues.
• Check Power Supply:
• Ensure that the BCM is receiving the correct voltage and ground. Use a multimeter to check the power supply to the BCM.
• Look for blown fuses that may affect the BCM or related circuits.
• Test the BCM:
• If possible, test the BCM for proper operation. This may involve using a scan tool to check for BCM functionality or replacing it with a known good unit to see if the problem persists.
• Inspect Other Modules:
• Check the other modules that communicate with the BCM. If one of these modules is malfunctioning, it can cause communication errors.
• Look for any signs of damage or issues with the wiring harnesses connecting these modules.
• Perform a Network Test:
• Use a scan tool capable of performing a network test to check for communication between the BCM and other modules. This can help identify if the issue is isolated to the BCM or if it involves other components.
• Clear Codes and Test Drive:
• After performing any repairs or inspections, clear the trouble codes and take the vehicle for a test drive to see if the code reappears.
• Check for Software Updates:
• Sometimes, communication issues can be resolved with a software update for the BCM or other modules. Check with the manufacturer for any available updates.
• Consult Technical Service Bulletins (TSBs):
• Look for any TSBs related to the U1520 code for your specific vehicle make and model. Manufacturers may have specific recommendations or known fixes for this issue.
• 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 and repair. By following these steps, you can systematically identify and resolve the communication error associated with the U1520 code.