U1739 – Module Communication Failure

The ODBII code U1739 indicates a “Module Communication Failure,” meaning there is a problem with communication between vehicle control modules, often due to a wiring issue, a faulty module, or a network problem.

The severity of ODBII code U1739 is moderate.

Common Causes For: U1738 U1738: Control Module Communication Failure

• Faulty wiring or connectors
• Failed or malfunctioning control module
• Poor ground connections
• Corroded or damaged pins in connectors
• Communication network issues (e.g., CAN bus problems)
• Software or firmware issues in modules
• Intermittent electrical connections
• Low battery voltage or power supply issues

Common misdiagnosis for U1739 U1739: “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 U1739 indicates a “Module Communication Failure,” which typically means that there is a problem with communication between various control modules in the vehicle. 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 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.
• Verify that the fuses related to the communication network are intact.
• Test Communication Lines:
• Use a scan tool to check the communication lines (CAN bus, LIN bus, etc.) for continuity and proper signal levels.
• If you have access to an oscilloscope, you can check the waveform of the communication signals.
• Inspect Modules:
• If possible, check the affected modules for any signs of physical damage or water intrusion.
• If you suspect a specific module is faulty, you may consider swapping it with a known good module to see if the issue persists.
• Reset the Modules:
• Sometimes, simply resetting the modules can resolve communication issues. This can be done by disconnecting the battery for a few minutes or using a scan tool to clear the codes.
• Check for Software Updates:
• Verify if there are any software updates available for the vehicle’s control modules. Sometimes, manufacturers release updates to fix communication issues.
• Perform a Network Test:
• Some advanced scan tools can perform a network test to check the integrity of the communication network. This can help identify if a specific module is not responding.
• Consult Wiring Diagrams:
• Refer to the vehicle’s service manual for wiring diagrams and communication protocols to better understand how the modules are interconnected.
• Professional Diagnosis:
• If the issue persists after performing the above steps, it may be necessary to consult a professional technician or dealership for further diagnosis. They may have specialized tools and knowledge to pinpoint the problem. By following these steps, you should be able to identify the cause of the U1739 code and take appropriate action to resolve the communication failure.