WOMS
U code network Medium severity

U1985 U1985: "Module Communication Failure

The OBD2 code U1985 indicates a "Module Communication Failure," meaning there is a problem with communication between vehicle control modules, which may affect their ability to share data or function properly

Definition

The OBD2 code U1985 indicates a "Module Communication Failure," meaning there is a problem with communication between vehicle control modules, which may affect their ability to share data or function properly

Common causes

  • Faulty wiring or connectors
  • Malfunctioning control module
  • Poor ground connections
  • Corrupted software or firmware
  • Intermittent electrical issues
  • Low battery voltage
  • Communication network issues (e.g., CAN bus problems)
  • Incompatible or missing modules

Common misdiagnoses

  • Faulty wiring or connectors
  • Defective control module
  • Software issues or updates needed
  • Battery or power supply problems
  • Grounding issues
  • Intermittent communication issues
  • Other communication protocol failures
  • Sensor malfunctions

Troubleshooting steps

  1. 1. Check for Other Codes

    Use an OBD-II scanner to check for any other trouble codes that may be present. Sometimes, multiple codes can provide more context for the issue

  2. 2. Inspect Wiring and Connectors

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

  4. 4. Pay special attention to the ground connections, as poor grounding can lead to communication issues

  5. 5. Check Power Supply

    Ensure that the affected modules are receiving the proper voltage. Use a multimeter to check the power supply to the modules

  6. 6. Test Communication Lines

  7. 7. Use a scan tool to check if you can communicate with the affected module. If you cannot, it may indicate a problem with the module itself or the communication lines

  8. 8. If possible, use an oscilloscope to check the data lines for proper signals

  9. 9. Inspect the CAN Bus

    If your vehicle uses a Controller Area Network (CAN) bus for communication, check for issues on the bus

  10. 10. Look for short circuits or open circuits in the CAN wiring

  11. 11. Check for termination resistors at both ends of the CAN bus; they should be present and functioning correctly

  12. 12. Check for Module Malfunction

    If the wiring and connections are good, the issue may lie with the module itself. Consider

  13. 13. Testing the module in another vehicle (if possible) to see if it functions correctly

  14. 14. Replacing the module if it is determined to be faulty

  15. 15. Software Updates

    Check if there are any software updates available for the vehicle's modules. Sometimes, communication issues can be resolved with a software update

  16. 16. 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 reappears

  17. 17. Consult Technical Service Bulletins (TSBs)

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

  18. 18. Seek Professional Help

    If the problem persists after performing these steps, it may be necessary to consult a professional mechanic or technician who has experience with the specific vehicle and its systems. By following these troubleshooting steps, you can systematically identify and resolve the underlying cause of the U1985 code