U2279 – Control Module Communication Bus Off.

The ODBII code U2279 indicates a communication issue where a control module is not able to communicate over the vehicle’s communication bus, often due to a fault in the module or wiring.

The severity of ODBII code U2279 is moderate to severe.

Common Causes For: U2277 U2277: Control Module Communication Bus Fault

• Faulty control module
• Damaged wiring or connectors
• Poor ground connections
• Communication bus short circuit
• Open circuit in the communication bus
• Corroded connectors
• Software issues or firmware corruption
• Interference from aftermarket devices
• Low battery voltage or power supply issues
• Faulty CAN bus transceiver

Common misdiagnosis for U2279 Control Module Communication Bus Off.

• Faulty control module
• Wiring issues
• Poor ground connections
• Corrupted software/firmware
• Faulty connectors or terminals
• Battery or power supply issues
• Intermittent communication faults
• Other communication bus errors (e.g., CAN bus issues)

Common Troubleshooting Steps

The OBD-II code U2279 indicates a communication issue on the control module communication bus, specifically that a control module is “off” or not communicating properly. This can be caused by various issues, including wiring problems, module failures, or configuration issues. Here are some common troubleshooting steps to diagnose and resolve the U2279 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 associated with the control modules on the communication bus. Look for:
• Damaged or frayed wires
• Corroded or loose connectors
• Signs of water intrusion or other environmental damage
• Check Power and Ground: Ensure that the affected control module has proper power and ground connections. Use a multimeter to verify voltage and ground continuity.
• Test the Control Module: If possible, test the affected control module to see if it is functioning correctly. This may involve:
• Replacing the module with a known good one
• Performing a bench test if applicable
• Inspect the Communication Bus: Check the integrity of the communication bus (CAN bus, LIN bus, etc.) for shorts, opens, or other issues. This may involve:
• Using an oscilloscope to monitor the bus signals
• Checking for proper termination resistors
• Check for Software Updates: Verify if there are any software updates available for the control modules. Sometimes, communication issues can be resolved with a software update.
• Clear Codes and Test Drive: After performing any repairs or checks, clear the trouble codes and take the vehicle for a test drive to see if the code returns.
• Consult Technical Service Bulletins (TSBs): Look for any TSBs related to the specific make and model of the vehicle. Manufacturers may have known issues and recommended fixes for communication problems.
• Professional Diagnosis: If the issue persists after performing the above steps, consider seeking help from a professional mechanic or dealership with advanced diagnostic tools.
• Document Findings: Keep a record of all findings, repairs, and tests performed. This can be helpful for future reference or if further diagnosis is needed. By following these steps, you should be able to identify and resolve the underlying issue causing the U2279 code.