U002C High Speed CAN Communication Bus Off

Definition

Common causes

• Faulty CAN bus wiring or connectors
• Short circuit in the CAN bus
• Open circuit in the CAN bus
• Faulty CAN bus module or ECU
• Interference from other electrical components
• Low battery voltage
• Corroded or damaged terminals
• Software or firmware issues in the ECU
• Faulty termination resistors
• Grounding issues in the vehicle's electrical system

Common misdiagnoses

• Faulty ABS module
• Defective engine control module (ECM)
• Bad wiring or connectors
• Malfunctioning body control module (BCM)
• Issues with the transmission control module (TCM)
• Faulty sensors (e.g., wheel speed sensors)
• Power supply issues
• Grounding problems
• Faulty diagnostic tools or software errors
• Incorrectly interpreted codes or symptoms

Troubleshooting steps

1. 1. Check for Additional Codes

   Use an OBD-II scanner to check for any other trouble codes that may be present. Other codes can provide additional context for the problem

2. 2. Inspect Wiring and Connectors

   Visually inspect the wiring and connectors associated with the High-Speed CAN bus. Look for signs of damage, corrosion, or loose connections

3. 3. Pay special attention to the connectors at the Engine Control Module (ECM), Transmission Control Module (TCM), and any other modules that communicate on the High-Speed CAN bus

4. 4. Check for Short Circuits or Open Circuits

   Use a multimeter to check for continuity in the CAN bus wires. Look for any short circuits or open circuits that could disrupt communication

5. 5. Measure the resistance between the CAN High and CAN Low wires. They should typically have a specific resistance value (usually around 60 ohms)

6. 6. Inspect Modules

   Check the modules that are connected to the High-Speed CAN bus. If one module is malfunctioning, it can cause communication issues

7. 7. If possible, test the modules by swapping them with known good units to see if the problem persists

8. 8. Check for Interference

   Look for any aftermarket devices or modifications that may interfere with the CAN bus communication, such as alarms, stereo systems, or other electronic devices

9. 9. Scan for Communication Issues

   Use a professional-grade scan tool to monitor the CAN bus communication. Check if all modules are communicating properly

10. 10. Some scan tools allow you to view live data from the modules, which can help identify which module is not responding

11. 11. Inspect the CAN Bus Termination Resistors

    Ensure that the CAN bus has the correct termination resistors (typically 120 ohms) at both ends of the bus. A missing or faulty resistor can cause communication issues

12. 12. Check Battery and Ground Connections

    Ensure that the vehicle's battery is in good condition and that all ground connections are secure. Poor power or ground can lead to communication failures

13. 13. Perform a Hard Reset

    Disconnect the vehicle's battery for a few minutes to reset the modules. Reconnect the battery and see if the code returns

14. 14. 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 the CAN bus.1

15. 15. Seek Professional Help

    If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or automotive technician who has experience with CAN bus systems. By following these troubleshooting steps, you can systematically identify and resolve the issue causing the U002C code