U1934 – Module Communication Failure

The ODBII code U1934 indicates a “Module Communication Failure,” meaning there is a problem with communication between the vehicle’s control modules, often due to a fault in the wiring, connectors, or the modules themselves.

The severity of ODBII code U1934 is moderate.

Common Causes For: U1931 U1931: “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 power supply issues
• Communication network issues (e.g., CAN bus problems)

Common misdiagnosis for U1934 U1934: “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 U1934 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: Start by scanning the vehicle for any other diagnostic trouble codes (DTCs). Sometimes, U1934 may be accompanied by other codes that can provide additional context for the issue.
• Inspect Wiring and Connectors: Examine the wiring and connectors associated with the affected modules. Look for signs of damage, corrosion, loose connections, or broken wires. Pay special attention to the communication lines (CAN bus) between modules.
• Check Power and Ground: Ensure that the affected module has proper power and ground connections. Use a multimeter to verify voltage and ground continuity.
• Test the Affected Module: If possible, test the module that is reporting the U1934 code. This may involve bench testing or swapping with a known good module to see if the problem persists.
• Inspect the CAN Bus: If the vehicle uses a Controller Area Network (CAN) for communication, check the integrity of the CAN bus. Look for short circuits, open circuits, or excessive resistance in the communication lines.
• Check for Interference: Sometimes, aftermarket accessories or modifications can interfere with module communication. Disconnect any non-factory equipment and see if the code clears.
• Update Software/Firmware: In some cases, a software update for the vehicle’s modules may be necessary. Check with the manufacturer or a qualified technician to see if updates are available.
• Perform a Hard Reset: Disconnect the vehicle’s battery for a few minutes to reset the modules. Reconnect the battery and see if the code reappears.
• Consult Technical Service Bulletins (TSBs): Check for any TSBs related to U1934 for your specific vehicle make and model. Manufacturers may have issued guidance on common issues and fixes.
• Seek Professional Help: If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or dealership with advanced diagnostic tools to further investigate the problem. By following these steps, you can systematically identify and address the underlying cause of the U1934 code.