U2685 – Control Module Communication Bus Fault

The ODBII code U2685: Control Module Communication Bus Fault indicates a communication issue between control modules in a vehicle’s network, suggesting that one or more modules are not properly communicating with each other.

The severity of ODBII code U2685 is moderate.

Common Causes For: U2684 Invalid Data Received from Vehicle Dynamics Control Module.

• Faulty control module
• Damaged wiring or connectors
• Poor ground connections
• Short circuits in the communication bus
• Interference from other electronic devices
• Corroded connectors
• Software issues or bugs in the control module
• Low battery voltage or power supply issues
• Faulty or malfunctioning sensors
• Incompatible aftermarket components or modifications

Common misdiagnosis for U2685 U2685: Control Module Communication Bus Fault

• Faulty control module
• Wiring issues
• Poor ground connections
• Corrupted software/firmware
• Faulty sensors
• Battery or power supply problems
• Communication network issues (CAN bus)
• Intermittent connection faults

Common Troubleshooting Steps

The OBD-II code U2685 indicates a “Control Module Communication Bus Fault.” This code typically points to a problem with the communication between various control 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. Other codes can provide context and help identify the root cause of the communication issue.
• Inspect Wiring and Connectors: Visually inspect the wiring and connectors associated with the control modules. Look for signs of damage, corrosion, loose connections, or frayed wires.
• Pay special attention to the connectors for the modules involved in the communication bus.
• Check the Control Modules: Ensure that all control modules are functioning properly. If a specific module is malfunctioning, it may disrupt communication on the bus.
• If possible, test the modules individually to confirm they are operational.
• Test the Communication Bus: Use a multimeter or an oscilloscope to check the voltage levels and signals on the communication bus (e.g., CAN bus).
• Look for any irregularities in the signal that could indicate a fault.
• Inspect for Short Circuits or Open Circuits: Check for short circuits or open circuits in the wiring harnesses that connect the control modules. This can often be a cause of communication faults.
• Check for Ground Issues: Ensure that all control modules have a good ground connection. Poor grounding can lead to communication problems.
• Update Software/Firmware: Check if there are any software or firmware updates available for the control modules. Sometimes, communication issues can be resolved with an update.
• Clear Codes and Test Drive: After performing any repairs or adjustments, 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 issues related to communication faults.
• Seek Professional Help: If the issue persists after performing the above steps, it may be necessary to consult a professional mechanic or technician who has experience with the specific vehicle and its control systems. By following these troubleshooting steps, you can systematically identify and resolve the underlying cause of the U2685 code.