U1374 – Communication Bus Off.

The ODBII code U1374 indicates a communication issue where the vehicle’s communication bus is offline or not functioning properly, often related to a failure in the network that connects various control modules.

The severity of ODBII code U1374 is moderate to severe.

Common Causes For: U1373 Invalid Data Received from Vehicle Control Module.

• Faulty wiring or connectors in the communication bus.
• Malfunctioning control modules.
• Poor ground connections.
• Short circuits in the communication lines.
• Interference from aftermarket devices.
• Software issues or bugs in the control modules.
• Low battery voltage or power supply issues.

Common misdiagnosis for U1374 Communication Bus Off.

• Faulty ABS module
• Defective engine control module (ECM)
• Bad wiring or connectors
• Malfunctioning body control module (BCM)
• Incorrectly diagnosed transmission issues
• Powertrain control module (PCM) failure
• Battery or charging system problems
• Faulty sensors or actuators
• Communication issues with other modules
• Software or firmware glitches

Common Troubleshooting Steps

The OBD-II code U1374 indicates a “Communication Bus Off” issue, which typically means that there is a problem with the communication between various modules in the vehicle’s network. 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: Examine the wiring and connectors related to the communication bus (CAN bus). Look for signs of damage, corrosion, or loose connections. Pay special attention to the connectors at the modules involved in the communication.
• Check for Short Circuits: Use a multimeter to check for short circuits in the wiring. A short can disrupt communication between modules.
• Inspect Modules: Check the modules that are part of the communication network. Ensure they are functioning properly and are not damaged. If possible, test the modules individually.
• Battery Voltage and Ground: Ensure that the vehicle’s battery is fully charged and that all ground connections are secure. Low voltage or poor grounding can cause communication issues.
• Scan Tool Communication: Use a scan tool to check if you can communicate with all modules. If some modules are unresponsive, it may indicate a problem with those specific modules or their connections.
• Check for Interference: Look for any aftermarket devices or modifications that may interfere with the communication bus. This includes alarms, stereo systems, or other electronic devices.
• Clear Codes and Test Drive: After performing checks and repairs, clear the trouble codes and take the vehicle for a test drive to see if the code returns.
• Consult Technical Service Bulletins (TSBs): Check for any TSBs related to the U1374 code for your specific vehicle make and model. Manufacturers may have specific recommendations or known issues.
• Professional Diagnosis: If the issue persists after performing the above steps, consider seeking help from a professional mechanic or dealership. They may have specialized tools and knowledge to diagnose complex communication issues. By following these steps, you can systematically identify and resolve the underlying cause of the U1374 code.