WOMS
U code network Medium severity

U1933 Module Communication Fault

The OBD2 code U1933: Module Communication Fault indicates a communication issue between vehicle modules, suggesting that one or more modules are not properly exchanging data

Definition

The OBD2 code U1933: Module Communication Fault indicates a communication issue between vehicle modules, suggesting that one or more modules are not properly exchanging data

Common causes

  • Faulty wiring or connectors
  • Malfunctioning control module
  • Corrupted software or firmware in the module
  • Poor ground connections
  • Interference from aftermarket devices
  • Low battery voltage
  • Communication network issues (e.g., CAN bus problems)
  • Damaged or corroded pins in connectors

Common misdiagnoses

  • Faulty wiring or connectors
  • Defective control module
  • Software issues or firmware corruption
  • Power supply problems
  • Grounding issues
  • Intermittent communication faults
  • Incorrectly configured or programmed modules
  • Other communication protocol errors

Troubleshooting steps

  1. 1. Check for Other Codes

  2. 2. Use an OBD-II scanner to check for any additional trouble codes. Other codes may provide more context or indicate which module is having communication issues

  3. 3. Inspect Wiring and Connectors

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

  5. 5. Pay special attention to ground connections, as poor grounding can lead to communication faults

  6. 6. Check Module Power Supply

  7. 7. Ensure that the affected modules are receiving the correct voltage and ground. Use a multimeter to check for proper voltage at the module connectors

  8. 8. Test Communication Lines

  9. 9. Use a scan tool to check the communication lines (CAN bus, LIN bus, etc.) for proper operation. You can use an oscilloscope to monitor the signal patterns on the communication lines

  10. 10. Look for any interruptions or irregularities in the communication signals

  11. 11. Inspect for Water Intrusion

  12. 12. Check for signs of water intrusion in the module areas, as moisture can cause communication issues. Look for rust or corrosion on connectors and modules

  13. 13. Perform a Module Reset

  14. 14. Sometimes, resetting the affected modules can resolve communication issues. Disconnect the battery for a few minutes or use a scan tool to clear the codes and reset the modules

  15. 15. Check for Software Updates

  16. 16. Verify if there are any software updates available for the vehicle's modules. Sometimes, manufacturers release updates to fix communication issues

  17. 17. Replace Faulty Modules

  18. 18. If a specific module is identified as faulty (e.g., through testing or if it is not responding), consider replacing it. Ensure that the replacement module is compatible with your vehicle

  19. 19. Consult Wiring Diagrams

  20. 20. Refer to the vehicle's service manual for wiring diagrams and communication protocols. This can help you trace the communication lines and identify potential issues

  21. 21. Seek Professional Help

  22. 22. If the issue persists after performing the above steps, it may be necessary to consult a professional technician or a dealership with advanced diagnostic tools to further investigate the problem. By following these troubleshooting steps, you can systematically identify and resolve the underlying cause of the U1933 code