U2377 – Control Module Communication Bus Off.

The ODBII code U2377 indicates a communication issue where a control module is unable to communicate on the vehicle’s communication bus, often due to a fault in the module or wiring.

The severity of ODBII code U2377 is moderate to severe.

Common Causes For: U2376 Control Module Communication Bus Off.

• Faulty control module
• Damaged wiring or connectors
• Poor ground connections
• Communication bus interference
• Software issues or bugs
• Low battery voltage
• Faulty or disconnected sensors
• Corroded terminals or connectors

Common misdiagnosis for U2377 Control Module Communication Bus Off.

• Faulty control module
• Wiring issues
• Poor ground connections
• Corrupted software/firmware
• Faulty sensors
• Battery or power supply issues
• Communication network problems
• Incorrectly installed aftermarket accessories

Common Troubleshooting Steps

The OBD-II code U2377 indicates a communication issue on the control module communication bus, specifically that a control module is “off” or not responding. This can be caused by various issues, including wiring problems, module failures, or software issues. Here are some common troubleshooting steps to diagnose and resolve the U2377 code:

• Check for Additional Codes: Use an OBD-II scanner to check for any other trouble codes that may be present. This can provide more context about the issue.
• Inspect Wiring and Connectors: Visually inspect the wiring and connectors related to the control modules on the communication bus. 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 control modules have the proper power supply. Use a multimeter to check voltage at the module connectors.
• Verify that fuses related to the control modules are intact.
• Test the Control Modules: If possible, test the affected control module(s) for functionality. This may involve using specialized diagnostic tools or swapping with a known good module.
• Check for any software updates or reprogramming that may be required for the control module.
• Inspect the Communication Bus: Check the integrity of the communication bus (CAN bus, LIN bus, etc.). Look for shorts, opens, or resistance issues in the bus wiring.
• Use an oscilloscope or a CAN bus analyzer to monitor the communication signals and ensure they are within specifications.
• Clear Codes and Test Drive: After performing inspections and repairs, clear the trouble codes using the OBD-II scanner.
• Take the vehicle for a test drive to see if the code reappears. Monitor the performance of the control modules during the drive.
• Check for Environmental Factors: Sometimes, environmental factors such as moisture or temperature can affect module performance. Ensure that the modules are not exposed to excessive moisture or heat.
• 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 the U2377 code.
• Seek Professional Help: If the issue persists after performing the above steps, it may be necessary to consult a professional technician or a dealership for further diagnosis. By following these troubleshooting steps, you can systematically identify and resolve the underlying issue causing the U2377 code.