WOMS
U code network Medium severity

U1391 U1391: ECM Communication Malfunction

The OBD2 code U1391: ECM Communication Malfunction indicates a communication issue between the Engine Control Module (ECM) and other control modules in the vehicle

Definition

The OBD2 code U1391: ECM Communication Malfunction indicates a communication issue between the Engine Control Module (ECM) and other control modules in the vehicle

Common causes

  • Faulty Engine Control Module (ECM)
  • Poor electrical connections or wiring issues
  • Corroded connectors
  • Faulty communication lines (CAN bus)
  • Malfunctioning sensors
  • Software issues or outdated firmware
  • Battery or charging system problems
  • Grounding issues
  • Interference from aftermarket devices or modifications

Common misdiagnoses

  • Faulty ECM (Engine Control Module)
  • Wiring issues or damaged connectors
  • Faulty sensors (e.g., crankshaft or camshaft position sensors)
  • Battery or charging system problems
  • Corrupted software or firmware in the ECM
  • Issues with other control modules (e.g., TCM, BCM)
  • Grounding issues
  • Faulty communication lines (CAN bus issues)

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

    Visually inspect the wiring and connectors related to the ECM and other modules. Look for signs of damage, corrosion, or loose connections

  3. 3. Pay special attention to the ground connections, as poor grounding can lead to communication issues

  4. 4. Check Power Supply

    Ensure that the ECM is receiving the proper voltage. Use a multimeter to check the power supply to the ECM and verify that it is within the manufacturer's specifications

  5. 5. Test the ECM

    If possible, test the ECM to ensure it is functioning correctly. This may involve using a scan tool to check for communication with the ECM or swapping it with a known good unit

  6. 6. Inspect Other Modules

    Check other control modules in the vehicle for communication issues. If one module is malfunctioning, it can affect communication with the ECM

  7. 7. Ensure that all modules are properly connected and functioning

  8. 8. Check for Short Circuits or Open Circuits

    Use a multimeter to check for short circuits or open circuits in the communication lines (CAN bus or other communication protocols) between the ECM and other modules

  9. 9. Look for Software Issues

    Sometimes, a software glitch can cause communication problems. Check if there are any available software updates for the ECM or other modules

  10. 10. Clear Codes and Test Drive

    After performing the above checks and repairs, clear the trouble codes using the OBD-II scanner and take the vehicle for a test drive to see if the code returns

  11. 11. Consult Technical Service Bulletins (TSBs)

    Check for any TSBs related to the specific make and model of the vehicle. Manufacturers may have issued guidance on common issues related to ECM communication

  12. 12. Seek Professional Help

    If the issue persists after performing the above steps, it may be necessary to consult a professional mechanic or technician who has experience with the specific vehicle and its systems. By following these troubleshooting steps, you can systematically identify and resolve the underlying cause of the U1391 code