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U code network High severity

U1104 Lost Communication with Vehicle Anti-Theft System (VATS) Module

The OBD2 code U1104 indicates a loss of communication with the Vehicle Anti-Theft System (VATS) module, which may affect the vehicle's ability to start or operate properly due to security system issues

Definition

The OBD2 code U1104 indicates a loss of communication with the Vehicle Anti-Theft System (VATS) module, which may affect the vehicle's ability to start or operate properly due to security system issues

Common causes

  • Faulty VATS module
  • Damaged wiring or connectors
  • Poor ground connection
  • Faulty ignition switch
  • Malfunctioning key or key fob
  • Corroded terminals
  • Issues with the vehicle's body control module (BCM)
  • Software or programming issues
  • Battery voltage problems
  • Interference from aftermarket devices

Common misdiagnoses

  • Faulty ignition switch
  • Bad battery or poor battery connections
  • Malfunctioning key or key fob
  • Defective anti-theft system components
  • Wiring issues or damaged connectors
  • Faulty body control module (BCM)
  • Incorrectly programmed or cloned key
  • Issues with the engine control module (ECM)

Troubleshooting steps

  1. 1. Check for Additional 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

    Visual Inspection: Check the wiring and connectors related to the VATS module for any signs of damage, corrosion, or loose connections

  3. 3. Connector Pins

    Ensure that the pins in the connectors are not bent or corroded

  4. 4. Test the VATS Module

    If accessible, test the VATS module for proper operation. This may involve checking power and ground connections to the module

  5. 5. Consult the vehicle’s service manual for specific testing procedures

  6. 6. Check for Power and Ground

    Use a multimeter to verify that the VATS module is receiving the correct voltage and ground. If there is no power or ground, trace the circuit back to find the issue

  7. 7. Inspect the Anti-Theft System

    Ensure that the anti-theft system is functioning correctly. If the system is activated or malfunctioning, it may prevent communication with the VATS module

  8. 8. Check for Interference

    Look for any aftermarket devices or modifications that may interfere with the vehicle’s communication systems. This includes alarm systems, remote starters, or other electronic devices

  9. 9. Perform a Network Scan

    Use a professional-grade scan tool to perform a network scan of the vehicle’s communication bus. This can help identify if other modules are having communication issues

  10. 10. Reset the System

    Sometimes, simply disconnecting the battery for a few minutes can reset the system and clear temporary communication issues. After reconnecting, check if the code reappears

  11. 11. Update Software/Firmware

    Check if there are any software updates available for the vehicle’s ECU or VATS module. Sometimes, manufacturers release updates to fix communication issues

  12. 12. 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 issues with the VATS system.1

  13. 13. Replace the VATS Module

    If all other steps fail and the VATS module is determined to be faulty, consider replacing it. Ensure that the replacement module is compatible with the vehicle.1

  14. 14. Seek Professional Help

    If you are unable to resolve the issue, it may be best to consult a professional mechanic or dealership with experience in your vehicle’s make and model.Conclusion Always refer to the specific service manual for your vehicle for detailed procedures and specifications. Troubleshooting can vary significantly between different makes and models, so having the right information is crucial