U1303 – Module Communication Failure

The ODBII code U1303 indicates a “Module Communication Failure,” meaning there is a problem with communication between the vehicle’s control modules, often due to a wiring issue, a faulty module, or a network problem.

The severity of ODBII code U1303 is moderate.

Common Causes For: U1302 U1302: “Module Communication Failure”

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

Common misdiagnosis for U1303 U1303: “Module Communication Failure”

• Faulty wiring or connectors
• Defective control module
• Low battery voltage
• Grounding issues
• Intermittent communication issues
• Software glitches or updates needed
• Faulty sensors
• Corrupted data or configuration errors

Common Troubleshooting Steps

The OBD-II code U1303 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 U1303 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 Module Power Supply:
• Ensure that the affected modules are receiving the proper voltage and ground. Use a multimeter to check the power supply to the modules.
• If a module is not receiving power, trace the wiring back to the fuse box and check for blown fuses or damaged wiring.
• 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.
• Check for Module Malfunction:
• If the wiring and connections are good, the issue may be with the module itself. If possible, swap the suspected module with a known good one to see if the problem persists.
• Some modules may require reprogramming or calibration after replacement.
• Inspect for Intermittent Issues:
• Sometimes, communication failures can be intermittent. Pay attention to when the code appears (e.g., during specific driving conditions) and check for any patterns.
• Clear Codes and Test Drive:
• After performing any repairs or inspections, clear the trouble codes and take the vehicle for a test drive to see if the U1303 code returns.
• 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 communication issues.
• 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 address complex communication issues. By following these steps, you can systematically identify and resolve the underlying cause of the U1303 code.