WOMS
U code network High severity

U1871 U1871: Control Module Communication Failure

The OBD2 code U1871 indicates a communication failure between control modules in a vehicle, suggesting that one or more modules are not properly communicating with each other

Definition

The OBD2 code U1871 indicates a communication failure between control modules in a vehicle, suggesting that one or more modules are not properly communicating with each other

Common causes

  • Faulty control module
  • Damaged wiring or connectors
  • Poor ground connections
  • Communication network issues (e.g., CAN bus problems)
  • Corroded terminals
  • Software or firmware issues
  • Low battery voltage
  • Interference from aftermarket devices

Common misdiagnoses

  • Faulty control module
  • Wiring issues
  • Poor ground connections
  • Corrupted software/firmware
  • Faulty sensors
  • Battery or power supply problems
  • Intermittent communication issues
  • Incorrectly installed aftermarket components

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 context and help pinpoint the issue

  2. 2. Inspect Wiring and Connectors

    Visually inspect the wiring and connectors associated with the control modules. Look for signs of damage, corrosion, or loose connections

  3. 3. Pay special attention to the wiring harnesses that connect the affected modules

  4. 4. Check Power and Ground

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

  5. 5. Verify that fuses related to the control modules are intact

  6. 6. Test Control Modules

    If possible, test the affected control modules individually to ensure they are functioning correctly. This may involve using specialized diagnostic tools or software

  7. 7. If a module is found to be faulty, it may need to be repaired or replaced

  8. 8. Check for Communication Issues

    Use a scan tool to monitor communication between modules. Check if the modules are responding as expected

  9. 9. Look for any communication errors or timeouts that may indicate a problem

  10. 10. Inspect the CAN Bus

    If your vehicle uses a Controller Area Network (CAN) bus, check for issues with the bus itself. Look for short circuits, open circuits, or interference

  11. 11. Use an oscilloscope or a CAN bus analyzer to check the signal integrity on the bus

  12. 12. Reset the Codes

    After performing inspections 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

  13. 13. Consult Technical Service Bulletins (TSBs)

    Check for any TSBs related to the specific make and model of your vehicle. Manufacturers may have issued guidance on common issues related to U1871

  14. 14. Seek Professional Help

    If the issue persists after performing the above steps, consider seeking assistance from a qualified mechanic or automotive technician who has experience with your vehicle's make and model.Conclusion Troubleshooting a U1871 code can be complex due to the nature of control module communication. Following these steps systematically can help identify and resolve the underlying issue. Always refer to the vehicle's service manual for specific diagnostic procedures and specifications