U1388 – Module Communication Failure

The ODBII code U1388 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 U1388 is moderate.

Common Causes For: U1387 U1387: “Control Module Communication Failure”

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

Common misdiagnosis for U1388 U1388: “Module Communication Failure”

• Faulty wiring or connectors
• Defective control module
• Software issues or updates needed
• Power supply problems
• Grounding issues
• Intermittent communication issues
• Other module failures (e.g., ABS, BCM)
• Sensor malfunctions
• Corrupted data or configuration errors
• Environmental interference (e.g., moisture, corrosion)

Common Troubleshooting Steps

The OBD-II code U1388 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 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 Module Power Supply:
• Ensure that the affected module(s) are 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 power source.
• 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 an oscilloscope, you can check for proper signal waveforms on the communication lines.
• Inspect for Short Circuits:
• Check for any short circuits in the wiring that could be causing interference with communication.
• Look for pinched or frayed wires that may be making contact with other circuits.
• Check for Module Malfunction:
• If the wiring and connections are good, the module itself may be faulty. Consider testing or replacing the affected module.
• If you have access to a known good module, you can swap it out to see if the issue resolves.
• Clear Codes and Test Drive:
• After performing any repairs, clear the trouble codes using the OBD-II scanner and take the vehicle for a test drive to see if the code returns.
• Monitor the vehicle’s performance and check for any other symptoms.
• Consult Technical Service Bulletins (TSBs):
• Check for any TSBs related to the specific make and model of the vehicle. Manufacturers may have issued guidance on common issues related to module communication.
• Professional Diagnosis:
• If the issue persists after performing the above steps, it may be necessary to seek the help of a professional mechanic or dealership with advanced diagnostic tools. By following these steps, you should be able to identify and resolve the underlying cause of the U1388 code.