U2066 – Control Module Communication Bus Off.

The ODBII code U2066 indicates a communication issue where a control module is unable to communicate on the vehicle’s communication bus, often due to a fault in the module or wiring.

The severity of ODBII code U2066 is moderate to high.

Common Causes For: U2065 Control Module Communication Bus Off.

• Faulty control module
• Damaged wiring or connectors
• Poor ground connections
• Communication bus failure
• Short circuit in the communication lines
• Corroded connectors
• Software issues or bugs
• Battery voltage issues
• Intermittent faults in the network
• Faulty sensors or actuators on the bus

Common misdiagnosis for U2066 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
• Intermittent connection issues

Common Troubleshooting Steps

The OBD-II code U2066 indicates a communication issue on the control module communication bus, specifically that a module is “off” or not responding. This can be caused by various issues, including wiring problems, module failures, or issues with the communication bus itself. Here are some common troubleshooting steps to diagnose and resolve the U2066 code:

• 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 on the communication bus. Look for signs of damage, corrosion, or loose connections.
• Pay special attention to the ground connections, as poor grounding can lead to communication issues.
• Check the Control Modules: Identify the control module(s) that are part of the communication bus. This may include modules like the Engine Control Module (ECM), Transmission Control Module (TCM), Body Control Module (BCM), etc.
• If possible, test the affected module(s) for proper operation. This may involve using a scan tool to communicate with the module and check for any internal faults.
• Test the Communication Bus: Use a multimeter or an oscilloscope to check the voltage levels and signal integrity on the communication bus (e.g., CAN bus).
• Look for short circuits, open circuits, or abnormal voltage levels that could indicate a problem.
• Check for Interference: Ensure that there are no aftermarket devices or modifications that could be interfering with the communication bus. This includes things like alarms, stereo systems, or other electronic accessories.
• Perform a Hard Reset: Disconnect the vehicle’s battery for a few minutes to reset the control modules. Reconnect the battery and see if the code returns.
• Update or Reprogram Modules: If the vehicle manufacturer has released updates or reprogramming procedures for the affected control modules, follow those instructions to ensure that the modules are running the latest software.
• Consult Technical Service Bulletins (TSBs): Check for any TSBs related to the U2066 code or the specific modules in your vehicle. Manufacturers may have known fixes or recommendations for this issue.
• Replace Faulty Components: If a specific module is determined to be faulty after testing, it may need to be replaced. Ensure that any replacement module is properly programmed to the vehicle.
• 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 your vehicle’s make and model. By following these troubleshooting steps, you should be able to identify and resolve the underlying issue causing the U2066 code.