U2671 – Vehicle Communication Bus Malfunction

The ODBII code U2671: Vehicle Communication Bus Malfunction indicates a problem with the communication between various control modules in the vehicle, which may affect their ability to exchange data properly.

The severity of ODBII code U2671 is moderate.

Common Causes For: U2669 Lost Communication with the Steering Angle Sensor.

• Faulty wiring or connectors in the communication bus
• Malfunctioning control modules
• Corrupted software or firmware in control modules
• Poor ground connections
• Short circuits or open circuits in the communication lines
• Interference from aftermarket devices
• Damaged or defective OBD-II port
• Low battery voltage or power supply issues

Common misdiagnosis for U2671 U2671: Vehicle Communication Bus Malfunction

• Faulty ECM (Engine Control Module)
• Defective BCM (Body Control Module)
• Wiring issues or shorts in the communication bus
• Bad ground connections
• Faulty sensors or actuators
• Corrupted software or firmware in modules
• Battery or power supply issues
• Incorrectly installed aftermarket accessories or devices

Common Troubleshooting Steps

The OBD-II code U2671 indicates a “Vehicle Communication Bus Malfunction.” This code typically points to issues with the communication between various control modules in the vehicle. Here are some common troubleshooting steps to diagnose and resolve the 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 ECM (Engine Control Module), BCM (Body Control Module), and any other modules that may be involved.
• 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 Modules: If possible, test the individual control modules for proper operation. This may involve using specialized diagnostic tools or software to communicate with each module.
• Inspect the CAN Bus: Check the CAN bus for proper voltage levels. The typical voltage levels should be around 2.5V to 3.5V when the vehicle is on.
• Use an oscilloscope to monitor the CAN bus signals for any irregularities or noise.
• Check for Interference: Look for any aftermarket devices or modifications that may interfere with the vehicle’s communication systems, such as alarms, remote starters, or audio systems.
• Update Software/Firmware: Check if there are any software updates available for the vehicle’s control modules. Sometimes, updating the firmware can resolve communication issues.
• 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 returns.
• 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 specializes in automotive electronics. By following these troubleshooting steps, you can systematically identify and resolve the underlying cause of the U2671 code.