U1868 – Module Communication Fault

The ODBII code U1868 indicates a “Module Communication Fault,” which means there is a communication issue between the vehicle’s control modules, preventing them from exchanging data properly.

The severity of ODBII code U1868 is generally considered moderate.

Common Causes For: U1866 U1866: “Inter-Module Communication Failure”

• Faulty wiring or connectors
• Failed control module
• Corrupted software in the module
• Poor ground connections
• Intermittent communication issues
• Low battery voltage
• Faulty CAN bus network
• Damaged or corroded terminals

Common misdiagnosis for U1868 U1868: “Module Communication Fault”

• Faulty wiring or connectors
• Defective control modules
• Power supply issues
• Grounding problems
• Software glitches or updates needed
• Intermittent communication issues
• Other communication fault codes (e.g., U codes)

Common Troubleshooting Steps

The OBD-II code U1868 indicates a “Module Communication Fault,” which typically means that there is a problem with communication between various modules in the vehicle’s network. 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 wiring harnesses that connect the modules, as these can be prone to wear and tear.
• Check Power and Ground:
• Ensure that the affected modules are receiving proper power and ground. Use a multimeter to check voltage and ground continuity.
• If a module is not receiving power, trace the circuit back to the fuse box and check for blown fuses or damaged wiring.
• Test the Modules:
• If possible, test the affected modules individually to ensure they are functioning correctly. This may involve using specialized diagnostic tools or software.
• If a module is found to be faulty, it may need to be repaired or replaced.
• Check for Communication Issues:
• Use a scan tool to monitor communication between modules. Look for any modules that are not responding or are showing communication errors.
• If a specific module is not communicating, it may be the source of the problem.
• Inspect the CAN Bus:
• The Controller Area Network (CAN) bus is responsible for communication between modules. Check for any issues with the CAN bus wiring, such as shorts or opens.
• Use an oscilloscope or a CAN bus diagnostic tool to analyze the signal on the bus.
• Reset the Modules:
• Sometimes, resetting the modules can clear communication faults. Disconnect the battery for a few minutes or use a scan tool to clear the codes and see if the issue persists.
• Update Software/Firmware:
• Check if there are any software or firmware updates available for the vehicle’s modules. Sometimes, communication issues can be resolved with an update.
• 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 known communication issues.
• Seek Professional Help:
• If the issue persists after performing the above steps, it may be necessary to consult a professional mechanic or dealership with experience in diagnosing complex electrical issues. By following these steps, you can systematically identify and resolve the underlying cause of the U1868 code.