WOMS
U code network Medium severity

U1979 U1979: "Module Communication Failure

The OBD2 code U1979 indicates a "Module Communication Failure," meaning there is a problem with communication between vehicle control modules, often due to a fault in the wiring, connectors, or the modules themselves

Definition

The OBD2 code U1979 indicates a "Module Communication Failure," meaning there is a problem with communication between vehicle control modules, often due to a fault in the wiring, connectors, or the modules themselves

Common causes

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

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

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 module(s). 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 module is receiving the proper voltage and ground. Use a multimeter to check the power supply to the module

  6. 6. Test the Module

    If possible, test the affected module to ensure it is functioning correctly. This may involve using specialized diagnostic tools or swapping the module with a known good one

  7. 7. Inspect the CAN Bus

  8. 8. The Controller Area Network (CAN) bus is responsible for communication between modules. Check for any faults in the CAN bus wiring

  9. 9. Use an oscilloscope or a CAN bus diagnostic tool to monitor the bus for proper signals

  10. 10. Check for Interference

    Look for any aftermarket devices or modifications that may be interfering with the communication between modules

  11. 11. Reset the Modules

    Sometimes, simply resetting the modules can resolve communication issues. Disconnect the battery for a few minutes, then reconnect it and see if the code returns

  12. 12. Update Software/Firmware

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

  13. 13. 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 known communication issues

  14. 14. Professional Diagnosis

    If the issue persists after performing the above steps, it may be necessary to seek help from a professional mechanic or dealership with advanced diagnostic equipment. By following these steps, you can systematically identify and address the root cause of the U1979 code