U2077 – Control Module Communication Bus Off.

The ODBII code U2077 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 OBDII code U2077 is moderate to severe.

Common Causes For: U2076 Control Module Communication Bus Off.

• 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 bugs in the control module
• Low battery voltage or power supply issues
• Interference from aftermarket devices or modifications
• Faulty or malfunctioning sensors on the bus

Common misdiagnosis for U2077 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
• Other communication bus errors
• Sensor malfunctions

Common Troubleshooting Steps

The OBD-II code U2077 indicates a communication issue between control modules in a vehicle, specifically that a control module is “bus off,” meaning it is not communicating properly on the CAN (Controller Area Network) bus. 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 related trouble codes. This can provide more context about the issue and help identify which module may be causing the problem.
• 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 bus wiring, which typically consists of a twisted pair of wires.
• 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 control module that is reporting the U2077 code. This may involve bench testing or swapping with a known good module to see if the problem persists.
• Inspect the CAN Bus: Use an oscilloscope or a CAN bus analyzer to check the signal integrity on the CAN bus. Look for any abnormalities in the signal, such as noise or voltage levels that are out of specification.
• Check for termination resistors (typically 120 ohms) at both ends of the CAN bus. If they are missing or faulty, it can cause communication issues.
• Check for Interference: Look for any aftermarket devices or modifications that may be interfering with the CAN bus communication. This includes things like alarms, remote starters, or other electronic accessories.
• Clear Codes and Test Drive: After performing any repairs or adjustments, clear the trouble codes using the OBD-II scanner and take the vehicle for a test drive to see if the code reappears.
• Consult Technical Service Bulletins (TSBs): Check for any manufacturer-specific TSBs related to the U2077 code or communication issues. There may be known fixes or updates available.
• Professional Diagnosis: If the issue persists after performing the above steps, consider seeking help from a professional mechanic or dealership with experience in diagnosing CAN bus communication issues.
• Software Updates: In some cases, a software update for the control modules may be necessary to resolve communication issues. Check with the manufacturer for any available updates. By following these troubleshooting steps, you can systematically identify and resolve the underlying cause of the U2077 code.