U2706 – Control Module Communication Bus Off.

The ODBII code U2706 indicates a communication issue where a control module is unable to communicate over the vehicle’s communication bus, often due to a fault in the module or wiring.

The severity of ODBII code U2706 is moderate to severe.

Common Causes For: U2705 Invalid Data Received from Vehicle Control Module.

• Faulty control module
• Poor electrical connections or wiring issues
• Short circuits in the communication bus
• Corroded connectors
• Faulty or damaged communication bus wiring
• Software or firmware issues in the control module
• Interference from aftermarket devices
• Low battery voltage or power supply issues

Common misdiagnosis for U2706 Control Module Communication Bus Off.

• Faulty control module
• Wiring issues
• Poor ground connections
• Corrupted software/firmware
• Faulty sensors
• Battery or power supply problems
• Communication network issues
• Intermittent connection problems

Common Troubleshooting Steps

The OBD-II code U2706 indicates a communication issue on the control module communication bus, specifically that a module is “off” or not communicating properly. This can be caused by various factors, including wiring issues, module failures, or problems with the communication bus itself. 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. This can provide more context about the issue.
• Inspect Wiring and Connectors: Visually inspect the wiring and connectors related to the control modules. Look for signs of damage, corrosion, or loose connections.
• Pay special attention to the communication bus wires (CAN bus) and ensure they are not pinched or shorted.
• Check Power and Ground: Verify that the affected control module has proper power and ground connections. Use a multimeter to check voltage and ground continuity.
• Ensure that the fuses related to the control modules are intact.
• Test the Control Module: If possible, test the control module in question. This may involve swapping it with a known good module or using a diagnostic tool to check its functionality.
• Some modules may have self-diagnostic capabilities that can provide more information.
• Inspect the Communication Bus: Use an oscilloscope or a CAN bus analyzer to check the communication signals on the bus. Look for any irregularities in the signal patterns.
• Ensure that the termination resistors are present and functioning correctly at both ends of the bus.
• Check for Interference: Look for any aftermarket devices or modifications that may be interfering with the communication bus. This includes alarms, remote starters, or other electronic devices.
• 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 common issues related to communication bus problems.
• Seek Professional Help: If the issue persists after performing the above steps, it may be necessary to consult a professional mechanic or technician with experience in automotive electronics and diagnostics. By following these troubleshooting steps, you can systematically identify and resolve the underlying cause of the U2706 code.