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U1071 Communication Bus Off

The OBD2 code U1071 indicates a communication issue where the vehicle's control module is unable to communicate with another module due to a bus-off condition, often related to a fault in the communication network

Definition

The OBD2 code U1071 indicates a communication issue where the vehicle's control module is unable to communicate with another module due to a bus-off condition, often related to a fault in the communication network

Common causes

  • Faulty or damaged wiring in the communication bus
  • Failed or malfunctioning control modules
  • Poor connections or corroded terminals in the wiring harness
  • 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 ABS module
  • Defective engine control module (ECM)
  • Bad wiring or connectors
  • Malfunctioning body control module (BCM)
  • Issues with the transmission control module (TCM)
  • Battery or charging system problems
  • Faulty sensors (e.g., wheel speed sensors)
  • Incorrectly diagnosed communication issues with other 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. This can provide more context about the issue

  2. 2. Inspect Wiring and Connectors

    Visually inspect the wiring and connectors related to 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 involved in the communication

  4. 4. Test the Communication Bus

    Use a multimeter or an oscilloscope to check the voltage levels on the CAN bus wires. The typical voltage should be around 2.5V when the bus is idle

  5. 5. Check for short circuits or open circuits in the communication lines

  6. 6. Check Control Modules

    Identify the control modules that are part of the communication network. This may include the Engine Control Module (ECM), Transmission Control Module (TCM), Body Control Module (BCM), etc

  7. 7. Ensure that all modules are functioning properly. If a module is faulty, it may need to be repaired or replaced

  8. 8. Inspect for Interference

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

  9. 9. Check for Ground Issues

    Ensure that all ground connections for the control modules are secure and free of corrosion. Poor grounding can lead to communication issues

  10. 10. Perform a Network Test

    Some advanced scan tools can perform a network test to check the integrity of the communication bus. This can help identify which module is causing the issue

  11. 11. Clear Codes and Test Drive

    After performing the above checks and repairs, clear the trouble codes using the OBD-II scanner and take the vehicle for a test drive to see if the code returns

  12. 12. Seek Professional Help

    If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or technician who has experience with automotive electronics and communication systems. By following these troubleshooting steps, you can systematically identify and resolve the underlying issue causing the U1071 code