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U code network High severity

U0071 Vehicle Communication Bus E (-) High

The OBD2 code U0071 indicates a communication issue within the vehicle's network, specifically that the Vehicle Communication Bus E is experiencing a high signal or voltage level, which may disrupt communication between...

Definition

The OBD2 code U0071 indicates a communication issue within the vehicle's network, specifically that the Vehicle Communication Bus E is experiencing a high signal or voltage level, which may disrupt communication between modules

Common causes

  • Faulty communication module
  • Damaged wiring or connectors
  • Short circuit in the communication bus
  • Open circuit in the communication bus
  • Corroded connectors
  • Faulty control modules
  • Software issues or bugs
  • Poor ground connections

Common misdiagnoses

  • Faulty Engine Control Module (ECM)
  • Faulty Transmission Control Module (TCM)
  • Bad wiring or connectors
  • Faulty Body Control Module (BCM)
  • Defective sensors
  • Battery or charging system issues
  • Faulty diagnostic tool or software
  • 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 associated with the communication bus E. Look for signs of damage, corrosion, or loose connections

  3. 3. Pay special attention to any connectors that may have been disturbed during repairs or maintenance

  4. 4. Check for Short Circuits

    Use a multimeter to check for short circuits in the wiring harness. Measure the resistance between the communication bus wires and ground to ensure there are no unintended connections

  5. 5. Test the Modules

    Identify which modules are connected to the communication bus E. Check if any of these modules are malfunctioning or have failed

  6. 6. If possible, perform a module reset or reprogramming to see if that resolves the issue

  7. 7. Inspect the Ground Connections

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

  8. 8. Check for Interference

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

  9. 9. Scan for Communication Issues

    Use a professional-grade scan tool to monitor the communication between modules. This can help identify if a specific module is not responding or is causing the issue

  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 pinpoint the source of the problem

  11. 11. Check Battery Voltage

    Ensure that the vehicle's battery is in good condition and fully charged. Low voltage can cause communication issues

  12. 12. Clear Codes and Test Drive

    After performing the above checks and repairs, clear the trouble codes and take the vehicle for a test drive to see if the code returns.1

  13. 13. 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 communication bus.1

  14. 14. Seek Professional Help

    If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or technician who specializes in automotive electronics. By following these troubleshooting steps, you can systematically identify and resolve the issue related to the U0071 code