U1338 – Control Module Communication Failure

The ODBII code U1338 indicates a “Control Module Communication Failure,” which means there is a problem with the communication between the vehicle’s control modules, potentially due to a wiring issue, a faulty module, or a network problem.

The severity of ODBII code U1338 is moderate.

Common Causes For: U1337 U1337: “Control Module Communication Fault”

• Faulty control module
• Damaged wiring or connectors
• Poor ground connections
• Corroded terminals
• Software issues or bugs
• Communication network failure (CAN bus issues)
• Intermittent electrical connections
• Low battery voltage or power supply issues

Common misdiagnosis for U1338 U1338: “Control Module Communication Failure”

• Faulty control module
• Wiring issues
• Poor ground connections
• Corrupted software/firmware
• Faulty sensors
• Battery or charging system problems
• Intermittent connection issues
• Communication network faults (CAN bus issues)

Common Troubleshooting Steps

The OBD-II code U1338 indicates a “Control Module Communication Failure.” This code typically suggests 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 Additional 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 control modules. Look for signs of damage, corrosion, or loose connections.
• Pay special attention to the wiring harnesses that connect the affected modules.
• Check Power and Ground: Ensure that the control modules have proper power and ground connections. Use a multimeter to check voltage and ground continuity.
• Verify that the fuses related to the control modules are intact.
• Test Control Modules: If possible, test the affected control modules individually. This may involve using specialized diagnostic tools or software to communicate with the modules.
• If a specific module is unresponsive, it may need to be replaced.
• Look for Intermittent Issues: Sometimes, communication failures can be intermittent. Check for any patterns or specific conditions under which the code appears (e.g., temperature, vehicle speed).
• Check for Software Updates: Verify if there are any software updates available for the vehicle’s control modules. Manufacturers sometimes release updates to fix communication issues.
• Clear Codes and Test Drive: After performing any repairs or checks, clear the codes using the OBD-II scanner and take the vehicle for a test drive to see if the code reappears.
• Consult Technical Service Bulletins (TSBs): Check for any TSBs related to the specific make and model of the vehicle. Manufacturers may have documented known issues and solutions for communication failures.
• Professional Diagnosis: If the issue persists after performing the above steps, consider seeking help from a professional mechanic or dealership. They may have access to advanced diagnostic tools and resources.
• Consider Environmental Factors: Sometimes, external factors such as moisture, temperature, or electromagnetic interference can affect communication between modules. Ensure that the vehicle is in a suitable environment for testing. By following these troubleshooting steps, you can systematically identify and resolve the underlying cause of the U1338 code.