U2647 – Vehicle Communication Bus Malfunction

The ODBII code U2647 indicates a malfunction in the vehicle communication bus, which affects the communication between various control modules in the vehicle.

The severity of ODBII code U2647 is moderate.

Common Causes For: U2646 Lost Communication with the Steering Angle Sensor.

• Faulty OBD-II connector
• Damaged wiring or connectors in the communication bus
• Malfunctioning ECU (Electronic Control Unit)
• Software issues or bugs in the vehicle’s control modules
• Poor ground connections
• Interference from aftermarket devices
• Corroded or loose pins in the connectors
• Faulty or incompatible diagnostic tool
• Issues with the vehicle’s battery or power supply
• Faulty communication modules (e.g., CAN bus modules)

Common misdiagnosis for U2647 Vehicle Communication Bus Malfunction

• Faulty ECM (Engine Control Module)
• Defective BCM (Body Control Module)
• Wiring issues or shorts in the communication lines
• Faulty sensors or actuators
• Issues with the CAN bus system
• Battery or power supply problems
• Corroded connectors or terminals
• Software or firmware issues in the vehicle’s modules

Common Troubleshooting Steps

The OBD-II code U2647 indicates a “Vehicle Communication Bus Malfunction.” This code typically points to issues with the communication between various modules in the vehicle, often related to the CAN (Controller Area Network) bus system. 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 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 CAN bus. Look for signs of damage, corrosion, or loose connections.
• Pay special attention to the connectors at the ECM (Engine Control Module), BCM (Body Control Module), and any other modules that communicate over the bus.
• Test the CAN Bus Voltage:
• Use a multimeter to check the voltage levels on the CAN High and CAN Low wires. The typical voltage should be around 2.5V when the bus is idle.
• If the voltage is significantly off, there may be a short or open circuit in the wiring.
• Check for Short Circuits:
• Inspect the CAN bus wiring for any shorts to ground or to each other. This can cause communication failures.
• Look for Faulty Modules:
• A malfunctioning module can disrupt communication on the bus. If you suspect a specific module, you can try disconnecting it to see if the code clears or if communication is restored.
• Scan for Module Communication:
• Use a scan tool to check if all modules are communicating properly. Some advanced scan tools can show you which modules are active and if there are any communication failures.
• Check for Software Updates:
• Sometimes, a software update for the vehicle’s modules can resolve communication issues. Check with the manufacturer for any available updates.
• Inspect Ground Connections:
• Ensure that all ground connections related to the modules are secure and free of corrosion. Poor grounding can lead to communication issues.
• Perform a Hard Reset:
• Disconnect the vehicle’s battery for a few minutes to reset the modules. Reconnect and see if the code reappears.
• Consult Technical Service Bulletins (TSBs):
• Check for any TSBs related to the U2647 code for your specific vehicle make and model. Manufacturers may have specific fixes or recommendations. 1
• Professional Diagnosis:
• If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or technician who has experience with your vehicle’s specific systems. By following these troubleshooting steps, you can systematically identify and resolve the underlying cause of the U2647 code.