U2779 – Vehicle Communication Bus Malfunction

The ODBII code U2779 indicates a malfunction in the vehicle communication bus, which affects the communication between various control modules in the vehicle.

The severity of ODBII code U2779 is generally considered moderate to severe.

Common Causes For: U2778 Vehicle Communication Bus Malfunction

• Faulty OBD-II connector
• Damaged wiring or connectors in the communication bus
• Malfunctioning control modules
• Poor ground connections
• Interference from aftermarket devices
• Software issues or bugs in the control modules
• Low battery voltage or power supply issues
• Corroded or loose pins in the connectors
• Faulty or damaged communication bus (CAN bus) lines
• Issues with the vehicle’s electrical system

Common misdiagnosis for U2779 Vehicle Communication Bus Malfunction

• Faulty Engine Control Module (ECM)
• Defective Body Control Module (BCM)
• Bad wiring or connectors
• Malfunctioning sensors
• Issues with the powertrain control module (PCM)
• Battery or charging system problems
• Incorrectly diagnosed transmission issues
• Faulty diagnostic tools or software errors

Common Troubleshooting Steps

The OBD-II code U2779 indicates a “Vehicle Communication Bus Malfunction.” This code typically points to issues with the communication between various modules in the vehicle, which can affect the overall functionality of the vehicle’s systems. 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:
• Visually inspect the wiring and connectors associated with the communication bus (CAN bus). Look for signs of damage, corrosion, or loose connections.
• Pay special attention to the connectors on the modules that are part of the communication network.
• Check for Short Circuits or Open Circuits:
• Use a multimeter to check for continuity in the communication lines. Look for any short circuits or open circuits that could disrupt communication.
• Test the resistance of the communication lines to ensure they are within specifications.
• Inspect Modules:
• Check the modules that are part of the communication network for any signs of failure. This may include the Engine Control Module (ECM), Transmission Control Module (TCM), Body Control Module (BCM), etc.
• If possible, perform a software update on the modules, as outdated software can sometimes cause communication issues.
• Check Power and Ground:
• Ensure that all modules have proper power and ground connections. A weak or intermittent power supply can lead to communication failures.
• Use a multimeter to verify voltage levels at the modules.
• Test the Communication Bus:
• Use a scan tool capable of monitoring live data to check if the modules are communicating properly. Look for any modules that are not responding.
• If available, use an oscilloscope to analyze the communication signals on the bus for any irregularities.
• Clear Codes and Test Drive:
• After performing the above checks 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 vehicle’s performance and any warning lights.
• 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 known issues related to communication bus malfunctions.
• Seek Professional Help:
• If the issue persists after performing the above steps, it may be necessary to consult a professional mechanic or technician who has experience with the specific vehicle make and model. By following these troubleshooting steps, you can systematically identify and resolve the underlying cause of the U2779 code.