U1267 Communication Bus Off

Definition

Common causes

• Faulty or damaged wiring in the communication bus
• Failed or malfunctioning control modules
• Poor connections or corroded terminals in the communication network
• Short circuits in the communication lines
• Interference from aftermarket devices or modifications
• Low battery voltage or power supply issues
• Faulty or damaged connectors

Common misdiagnoses

• Faulty ECM (Engine Control Module)
• Bad wiring or connectors
• Defective sensors
• Malfunctioning ABS module
• Issues with the body control module (BCM)
• Powertrain control module (PCM) failure
• Battery or charging system problems
• Faulty communication lines or networks
• Incorrectly installed aftermarket accessories
• Software or firmware issues in control modules

Troubleshooting steps

1. 1. Check for Additional Codes

   Use an OBD-II scanner to check for any other trouble codes that may be present. Addressing related codes can help pinpoint the issue

2. 2. 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

3. 3. Pay special attention to the connectors at the control modules and any junction points

4. 4. 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

5. 5. Test the resistance of the communication wires to ensure they are within specifications

6. 6. Inspect Control Modules

   Check the control modules (ECM, BCM, TCM, etc.) for any signs of damage or failure. If a module is malfunctioning, it may not communicate properly with the bus

7. 7. If possible, perform a software update or reset the modules to see if that resolves the issue

8. 8. Test the Communication Bus

   Use a scan tool capable of monitoring the communication bus to see if data is being transmitted between modules

9. 9. Check for proper voltage levels on the communication lines (typically around 2.5V to 3.5V for CAN bus)

10. 10. Check for Interference

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

11. 11. Perform a Battery Reset

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

12. 12. Consult Technical Service Bulletins (TSBs)

    Check for any TSBs related to the U1267 code for your specific vehicle make and model. Manufacturers may have specific fixes or recommendations

13. 13. Replace Faulty Components

    If a specific module is identified as faulty, consider replacing it. Ensure that any replacement modules are properly programmed and calibrated

14. 14. 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 should be able to identify and resolve the underlying issue causing the U1267 code