U2079 – Control Module Communication Bus Off.

The ODBII code U2079 indicates a communication issue where a control module is not able to communicate on the vehicle’s communication bus, often due to a fault in the module or wiring.

The severity of ODBII code U2079 is moderate to severe.

Common Causes For: U2078 Lost Communication with the Steering Angle Sensor Module.

• 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
• Intermittent electrical connections
• Faulty or incompatible aftermarket parts

Common misdiagnosis for U2079 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 U2079 indicates a communication issue between control modules in a vehicle, specifically that a control module is “Bus Off.” This typically means that the module has detected a fault in the communication bus and has stopped communicating to prevent further issues. Here are some common troubleshooting steps to diagnose and resolve the U2079 code:

• Check for Additional Codes: Use an OBD-II scanner to check for any other trouble codes that may be present. Other codes can provide context and help identify the root cause of the issue.
• Inspect Wiring and Connectors: Visually inspect the wiring and connectors associated with the control modules. Look for signs of damage, corrosion, or loose connections.
• Pay special attention to the CAN (Controller Area Network) bus wiring, as this is often where communication issues arise.
• Check for Short Circuits or Open Circuits: Use a multimeter to check for continuity in the CAN bus wiring. Look for any short circuits or open circuits that could disrupt communication.
• Check for proper voltage levels on the communication lines.
• Inspect Control Modules: Identify the control module that is reporting the U2079 code. Inspect it for physical damage or signs of water intrusion.
• If possible, test the control module in another vehicle to see if it functions correctly.
• Check for Software Updates: Verify if there are any software updates available for the control modules. Sometimes, manufacturers release updates to fix communication issues.
• Reset the Control Module: Clear the trouble codes using an OBD-II scanner and see if the code returns. Sometimes, a temporary glitch can cause communication issues.
• Test the Battery and Charging System: Ensure that the vehicle’s battery and charging system are functioning properly. Low voltage can cause communication issues between modules.
• Check for Ground Issues: Ensure that all ground connections for the control modules are secure and free of corrosion. Poor grounding can lead to communication failures.
• Perform a Network Test: If you have access to advanced diagnostic tools, perform a network test to check the integrity of the communication bus and identify any faults.
• Consult Technical Service Bulletins (TSBs): Check for any TSBs related to the U2079 code for your specific vehicle make and model. Manufacturers may have specific recommendations for addressing this issue.1
• Replace Faulty Components: If a specific control module is identified as faulty, consider replacing it. Ensure that the replacement module is compatible with your vehicle.1
• Seek Professional Help: If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or dealership for further diagnosis and repair. By following these troubleshooting steps, you can systematically identify and resolve the underlying issues causing the U2079 code.