U1931 – Module Communication Failure

The ODBII code U1931 indicates a “Module Communication Failure,” meaning there is a problem with communication between vehicle modules, often due to a fault in the wiring, connectors, or the modules themselves.

The severity of ODBII code U1931 is moderate.

Common Causes For: U1930 U1930: “Module Communication Failure”

• Faulty wiring or connectors
• Failed or malfunctioning control module
• Corrupted software or firmware in the module
• Poor ground connections
• Interference from aftermarket devices
• Low battery voltage or weak battery
• Communication network issues (e.g., CAN bus problems)
• Damaged or corroded pins in connectors

Common misdiagnosis for U1931 U1931: “Module Communication Failure”

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

Common Troubleshooting Steps

The OBD-II code U1931 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 module. 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 module is receiving the proper voltage and ground. Use a multimeter to check the power supply to the module.
• If the module is not receiving power, trace the wiring back to the fuse box and check for blown fuses or damaged wires.
• Test the Module:
• If possible, test the affected module by swapping it with a known good module (if applicable) to see if the problem persists.
• Some modules may have self-diagnostic capabilities that can provide additional information.
• Inspect the CAN Bus:
• If the vehicle uses a Controller Area Network (CAN) bus for communication, check the integrity of the CAN bus wiring. Look for shorts, opens, or interference.
• Use an oscilloscope to check the CAN bus signals if you have the necessary equipment and expertise.
• Check for Software Updates:
• Sometimes, communication issues can be resolved with a software update. Check with the vehicle manufacturer or a dealership to see if there are any available updates for the affected module.
• Clear Codes and Test Drive:
• After performing any repairs or inspections, clear the trouble 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 specific make and model of the vehicle. Manufacturers may have issued guidance on common communication issues.
• Professional Diagnosis:
• If the issue persists after performing the above steps, consider seeking help from a professional mechanic or dealership with experience in diagnosing module communication issues. By following these steps, you can systematically identify and resolve the underlying cause of the U1931 code.