WOMS
U code network High severity

U1790 refers to a communication issue between the engine control module (ECM) and the transmission control module (TCM)

The OBD2 code U1790 indicates a communication issue between the engine control module (ECM) and the transmission control module (TCM), suggesting a failure in data exchange between these two components

Definition

The OBD2 code U1790 indicates a communication issue between the engine control module (ECM) and the transmission control module (TCM), suggesting a failure in data exchange between these two components

Common causes

  • Faulty wiring or connectors between ECM and TCM
  • Failed ECM or TCM
  • Corrupted software or firmware in ECM or TCM
  • Poor ground connections
  • Electrical interference or noise
  • Blown fuses related to ECM or TCM
  • Faulty sensors affecting communication
  • Issues with the vehicle's CAN bus system

Common misdiagnoses

  • Faulty ECM
  • Faulty TCM
  • Wiring issues or shorts
  • Corroded connectors
  • Faulty sensors (e.g., speed sensors)
  • Transmission fluid issues
  • Battery or charging system problems
  • Software or firmware issues
  • Grounding issues
  • Faulty CAN bus communication components

Troubleshooting steps

  1. 1. Check for Additional Codes

    Use an OBD-II scanner to check for any other trouble codes that may be present. This can provide more context and help identify related issues

  2. 2. Inspect Wiring and Connectors

  3. 3. Visually inspect the wiring harness and connectors between the ECM and TCM for any signs of damage, corrosion, or loose connections

  4. 4. Ensure that all connectors are securely plugged in and that there are no bent pins

  5. 5. Check for Short Circuits or Open Circuits

  6. 6. Use a multimeter to test the wiring for continuity and to check for any short circuits or open circuits that could be causing communication issues

  7. 7. Inspect Ground Connections

  8. 8. Ensure that the ground connections for both the ECM and TCM are secure and free of corrosion. Poor grounding can lead to communication problems

  9. 9. Check Power Supply

  10. 10. Verify that both the ECM and TCM are receiving the correct voltage. Use a multimeter to check the power supply to both modules

  11. 11. Look for Software Updates

  12. 12. Check if there are any available software updates for the ECM or TCM. Sometimes, manufacturers release updates to fix communication issues

  13. 13. Perform a Hard Reset

  14. 14. Disconnect the battery for a few minutes to reset the ECM and TCM. Reconnect the battery and see if the code reappears

  15. 15. Inspect for Interference

  16. 16. Check for any aftermarket accessories or modifications that may be interfering with the communication between the ECM and TCM

  17. 17. Test the Modules

  18. 18. If all else fails, you may need to test the ECM and TCM individually to determine if one of the modules is faulty. This may require specialized diagnostic equipment

  19. 19. Consult Technical Service Bulletins (TSBs)

  20. 20. Look for any TSBs related to the specific make and model of the vehicle, as they may provide additional guidance on resolving U1790. 1

  21. 21. Seek Professional Help

  22. 22. If you are unable to resolve the issue after performing these steps, it may be best to consult a professional mechanic or technician who has experience with your vehicle's specific systems. By following these troubleshooting steps, you can systematically identify and address the communication issue indicated by the U1790 code