U1681 – Module Communication Failure

The ODBII code U1681 indicates a “Module Communication Failure,” meaning 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 U1681 is generally considered moderate.

Common Causes For: U1680 U1680: “Module Communication Failure”

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

Common misdiagnosis for U1681 U1681: “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 U1681 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, other codes can provide additional context for the U1681 code.
• 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.
• 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 a scope, you can check the signal waveforms on the communication lines to ensure they are functioning correctly.
• Inspect Modules:
• Identify which module is reporting the U1681 code. This may require checking the vehicle’s service manual for module locations and functions.
• If possible, test the module in question by swapping it with a known good module to see if the problem persists.
• Check for Software Updates: Sometimes, communication issues can be resolved with a software update. Check with the manufacturer or a dealership to see if there are any updates available for the affected modules.
• Clear Codes and Test Drive: After performing the above checks and repairs, 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): Check for any TSBs related to the U1681 code for your specific vehicle make and model. Manufacturers may have issued guidance on common issues and fixes.
• Professional Diagnosis: If the issue persists after performing the above steps, it may be necessary to seek the help of a professional technician who has experience with automotive electronics and communication systems. By following these steps, you should be able to identify and resolve the underlying issue causing the U1681 code.