U2379 – Control Module Communication Bus Off.

The ODBII code U2379 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 U2379 is moderate to severe.

Common Causes For: U2378 U2378: BECM Communication Fault

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

Common misdiagnosis for U2379 Control Module Communication Bus Off.

• Faulty control module
• Wiring issues
• Poor ground connections
• Corrupted software/firmware
• Faulty sensors
• Battery or power supply problems
• Communication network issues
• Intermittent connection problems

Common Troubleshooting Steps

The OBD-II code U2379 indicates a communication issue on the control module communication bus, specifically that a control module is “off” or not communicating properly. Here are some common troubleshooting steps to diagnose and resolve this issue:

• Check for Other Codes: Start by scanning the vehicle for any other diagnostic trouble codes (DTCs). Other codes may provide additional context or indicate related issues.
• Inspect Wiring and Connectors:
• Visually inspect the wiring and connectors associated with 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. If the voltage is low or absent, trace back to the power source.
• Test the Control Modules:
• If possible, test the affected control module(s) for functionality. This may involve using a scan tool to check for communication with the module.
• If the module is not responding, it may need to be replaced.
• Inspect the Communication Bus:
• Check the integrity of the communication bus (CAN bus, LIN bus, etc.). Look for short circuits, open circuits, or any other issues that could disrupt communication.
• Use an oscilloscope or a specialized scan tool to monitor the bus signals for proper voltage levels and waveforms.
• Check for Interference: Sometimes, aftermarket accessories or modifications can interfere with the communication bus. Disconnect any non-factory components and see if the issue persists.
• Perform a Hard Reset: Disconnect the vehicle’s battery for a few minutes to reset the control modules. Reconnect the battery and see if the code reappears.
• Update Software/Firmware: Check if there are any software updates available for the vehicle’s control modules. Sometimes, manufacturers release updates to fix communication issues.
• Consult Technical Service Bulletins (TSBs): Look for any TSBs related to the specific make and model of the vehicle. Manufacturers may have documented known issues and solutions.
• Seek Professional Help: If the issue persists after performing these steps, it may be necessary to consult a professional technician or dealership for further diagnosis. They may have access to specialized tools and resources. By following these steps, you should be able to identify and resolve the underlying issue causing the U2379 code.