U1938 – Module Communication Failure

The ODBII code U1938 indicates a “Module Communication Failure,” meaning there is a problem with communication between vehicle modules, often due to a fault in the wiring, connectors, or the modules themselves.

The severity of ODBII code U1938 is moderate.

Common Causes For: U1937 U1937: “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 U1938 U1938: “Module Communication Failure”

• Faulty wiring or connectors
• Defective control modules
• Software issues or updates needed
• Power supply problems
• Grounding issues
• Intermittent communication faults
• Incorrectly configured or programmed modules

Common Troubleshooting Steps

The OBD-II code U1938 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, multiple codes can provide more context for the issue.
• Inspect Wiring and Connectors:
• Visually inspect the wiring and connectors associated with the affected module(s). 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 module is receiving the proper voltage and ground. Use a multimeter to check the power supply to the module.
• If the module is not receiving power, trace the wiring back to the fuse box and check for blown fuses or damaged wires.
• Test the Module:
• If possible, test the affected module to ensure it is functioning correctly. This may involve using specialized diagnostic tools or swapping the module with a known good one.
• If the module is faulty, it may need to be repaired or replaced.
• Check for Communication:
• Use a scan tool to check if the affected module is communicating with other modules. If it is not, there may be a fault in the communication network.
• You can also use a scope or a multimeter to check the data lines for proper signals.
• Inspect the CAN Bus:
• If your vehicle uses a Controller Area Network (CAN) bus, check for issues with the bus itself. Look for short circuits, open circuits, or interference.
• You may need to use a CAN bus analyzer to diagnose communication issues.
• Reset the Codes:
• 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):
• Check for any manufacturer-specific TSBs related to U1938 or communication issues. There may be known fixes or updates available.
• Seek Professional Help:
• If you are unable to resolve the issue after these steps, consider seeking help from a qualified automotive technician or dealership. They may have access to advanced diagnostic tools and resources. By following these steps, you should be able to identify and resolve the underlying issue causing the U1938 code.