U1956 – Module Communication Failure

The ODBII code U1956 indicates a “Module Communication Failure,” meaning that there is a problem with communication between the vehicle’s control modules, which may affect their ability to share data or function properly.

The severity of ODBII code U1956 is moderate.

Common Causes For: U1955 Lost Communication with Body Control Module (BCM).

• Faulty wiring or connectors
• Malfunctioning control module
• Poor ground connections
• Corroded or damaged pins
• Intermittent communication issues
• Software or firmware issues
• Low battery voltage
• Electrical interference
• Aftermarket modifications or installations
• Faulty CAN bus system

Common misdiagnosis for U1956 U1956: “Module Communication Failure”

• Faulty wiring or connectors
• Defective control module
• Software issues or updates needed
• Battery or power supply problems
• Grounding issues
• Intermittent communication issues
• Other communication protocol failures

Common Troubleshooting Steps

The OBD-II code U1956 indicates a “Module Communication Failure,” which typically means that there is a problem with communication between the vehicle’s control modules. 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 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 associated with the affected modules. 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 Power Supply:
• Ensure that the affected modules are receiving the proper voltage. Use a multimeter to check the power supply to the modules.
• Verify that the fuses related to the communication network are intact.
• Test Communication Lines:
• Use a scan tool to check the communication lines (CAN bus, LIN bus, etc.) for continuity and proper voltage levels.
• If you have access to an oscilloscope, you can check for signal integrity on the communication lines.
• Inspect Modules:
• If possible, check the affected module for any signs of damage or malfunction. This may involve removing the module and inspecting it physically.
• If you suspect a module is faulty, you may need to replace it or reprogram it.
• Check for Interference:
• Look for any aftermarket devices or modifications that may interfere with the vehicle’s communication network. This includes alarm systems, stereo systems, or other electronic devices.
• Perform a Network Test:
• Some advanced scan tools can perform a network test to check the communication between modules. This can help identify which module is not communicating properly.
• Reset the System:
• After addressing any issues found, clear the trouble codes using the OBD-II scanner and see if the code returns after a test drive.
• 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 communication issues.
• 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 underlying cause of the U1956 code.