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U code network High severity

U1571 Communication Bus Off

The OBD2 code U1571 indicates a communication issue where a module on the vehicle's communication bus is not responding or is offline, potentially due to a fault in the wiring, connectors, or the module itself

Definition

The OBD2 code U1571 indicates a communication issue where a module on the vehicle's communication bus is not responding or is offline, potentially due to a fault in the wiring, connectors, or the module itself

Common causes

  • Faulty wiring or connectors in the communication bus
  • Malfunctioning control modules
  • Short circuits or open circuits in the bus lines
  • Interference from aftermarket devices
  • Software issues or bugs in the control modules
  • Low battery voltage or power supply issues
  • Corrosion or damage to connectors

Common misdiagnoses

  • Faulty ABS module
  • Defective engine control module (ECM)
  • Malfunctioning transmission control module (TCM)
  • Wiring issues or shorts in the communication lines
  • Bad ground connections
  • Faulty sensors
  • Incorrectly diagnosed battery or charging system issues
  • Issues with the body control module (BCM)

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. Look for signs of damage, corrosion, or loose connections

  3. 3. Pay special attention to the connectors of the modules involved in the communication network

  4. 4. Check Power and Ground

    Ensure that the affected modules have proper power and ground connections. Use a multimeter to verify voltage and ground continuity

  5. 5. Test the Communication Network

    Use a scan tool to monitor the communication between modules. Check if other modules are communicating properly

  6. 6. If possible, use an oscilloscope to check the signal integrity on the communication lines (CAN, LIN, etc.)

  7. 7. Inspect Modules

    Identify which module is reporting the U1571 code. If possible, test the module for proper operation

  8. 8. If the module is suspected to be faulty, consider replacing it or reprogramming it if necessary

  9. 9. Check for Short Circuits or Open Circuits

    Use a multimeter to check for short circuits or open circuits in the communication lines. This may involve checking continuity between modules

  10. 10. Look for Interference

    Check for any aftermarket devices or modifications that may interfere with the communication bus. This includes alarms, stereo systems, or other electronic devices

  11. 11. Clear Codes and Test Drive

    After performing any repairs or adjustments, clear the trouble codes and take the vehicle for a test drive to see if the code returns

  12. 12. 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 U1571 code

  13. 13. Seek Professional Help

    If the issue persists after performing the above steps, consider seeking help from a professional mechanic or dealership with experience in diagnosing communication issues. By following these steps, you should be able to identify and resolve the underlying issue causing the U1571 code