WOMS
U code network High severity

U2790 U2790: Control Module Communication Bus Fault

The OBD2 code U2790: Control Module Communication Bus Fault indicates a communication issue between control modules in the vehicle, suggesting that one or more modules are not properly communicating over the vehicle's...

Definition

The OBD2 code U2790: Control Module Communication Bus Fault indicates a communication issue between control modules in the vehicle, suggesting that one or more modules are not properly communicating over the vehicle's data bus

Common causes

  • Faulty control module
  • Damaged wiring or connectors
  • Poor ground connections
  • Corroded terminals
  • Intermittent electrical connections
  • Software issues or bugs
  • Faulty communication bus (CAN bus) components
  • Low battery voltage or power supply issues
  • Aftermarket modifications or installations affecting communication
  • Environmental factors (moisture, temperature extremes)

Common misdiagnoses

  • Faulty control module
  • Wiring issues or shorts
  • Poor ground connections
  • Corroded connectors
  • Battery or power supply problems
  • Software or firmware issues
  • Other communication bus faults (e.g., CAN bus issues)
  • Sensor malfunctions
  • Intermittent electrical connections
  • Incorrectly diagnosed related codes

Troubleshooting steps

  1. 1. Check for Additional Codes

    Use an OBD-II scanner to check for any other related trouble codes. Sometimes, multiple codes can provide more context about the issue

  2. 2. Inspect Wiring and Connectors

    Visual Inspection: Check the wiring and connectors associated with the control modules 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. Check the Control Modules

    Module Functionality: Verify that the control modules are functioning properly. If a specific module is malfunctioning, it may not communicate correctly with others

  5. 5. Reprogram or Reset

    If a module is suspected to be faulty, consider reprogramming or resetting it

  6. 6. Inspect the Communication Bus

    CAN Bus Integrity: Check the integrity of the CAN (Controller Area Network) bus. Use a multimeter to measure the voltage levels on the bus wires

  7. 7. Termination Resistors

    Ensure that the termination resistors are present and functioning correctly at both ends of the bus

  8. 8. Check for Short Circuits

    Use a multimeter to check for short circuits in the wiring harnesses connected to the control modules. A short can disrupt communication

  9. 9. Test the Battery and Ground Connections

    Battery Voltage: Ensure the vehicle's battery is fully charged and in good condition

  10. 10. Ground Connections

    Check all ground connections for the control modules to ensure they are clean and secure

  11. 11. Scan Tool Communication

    Use a professional scan tool to communicate with each control module individually. This can help identify which module is not responding

  12. 12. Look for Software Updates

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

  13. 13. Perform a Hard Reset

    Disconnect the vehicle's battery for a few minutes to reset the control modules. Reconnect and see if the code reappears

  14. 14. Consult Technical Service Bulletins (TSBs)

    Look for any TSBs related to the specific make and model of the vehicle. Manufacturers may have documented solutions for known issues.1

  15. 15. Seek Professional Help

    If the issue persists after performing the above steps, it may be necessary to consult a professional mechanic or technician who specializes in automotive electronics. By following these troubleshooting steps, you can systematically identify and resolve the underlying cause of the U2790 code