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U code network High severity

U1748 U1748: Transmission Control Module Communication Error

The OBD2 code U1748 indicates a communication error between the Transmission Control Module (TCM) and other control modules in the vehicle, suggesting a possible issue with wiring, connectors, or the TCM itself

Definition

The OBD2 code U1748 indicates a communication error between the Transmission Control Module (TCM) and other control modules in the vehicle, suggesting a possible issue with wiring, connectors, or the TCM itself

Common causes

  • Faulty Transmission Control Module (TCM)
  • Damaged wiring or connectors
  • Poor ground connections
  • Corrupted software or firmware in the TCM
  • Faulty Engine Control Module (ECM)
  • Communication network issues (CAN bus problems)
  • Low battery voltage or electrical issues
  • Corroded terminals or connectors

Common misdiagnoses

  • Faulty Transmission Control Module (TCM)
  • Wiring issues or damaged connectors
  • Faulty Engine Control Module (ECM)
  • Low transmission fluid levels
  • Transmission solenoid problems
  • Faulty sensors (e.g., speed sensors)
  • Software issues or outdated firmware
  • Battery or charging system problems
  • Grounding issues
  • Corrupted data in the vehicle's computer system

Troubleshooting steps

  1. 1. Check for Additional Codes

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

  2. 2. Inspect Wiring and Connectors

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

  3. 3. Repair or Replace

    If any damaged wires or connectors are found, repair or replace them as necessary

  4. 4. Check Power and Ground

    Power Supply: Ensure that the TCM is receiving the correct voltage. Use a multimeter to check the power supply to the TCM

  5. 5. Ground Connections

    Verify that the ground connections for the TCM are secure and free of corrosion

  6. 6. Inspect the CAN Bus

    Communication Lines: Check the Controller Area Network (CAN) bus lines for continuity and integrity. Look for shorts, opens, or high resistance in the communication lines

  7. 7. Termination Resistors

    Ensure that the CAN bus has the proper termination resistors in place

  8. 8. Check for Software Updates

    Manufacturer Updates: Check if there are any software updates available for the TCM or other related modules. Sometimes, manufacturers release updates to fix communication issues

  9. 9. Test the TCM

    Bench Test: If possible, remove the TCM and perform a bench test to ensure it is functioning correctly

  10. 10. Replacement

    If the TCM is found to be faulty, consider replacing it

  11. 11. Scan for Module Communication

    Network Scan: Use a professional-grade scan tool to perform a network scan and check if other modules are communicating properly. This can help identify if the issue is isolated to the TCM or if it affects other modules

  12. 12. 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 reappears

  13. 13. Consult Technical Service Bulletins (TSBs)

    Check for any TSBs related to the U1748 code for your specific vehicle make and model. Manufacturers may have specific recommendations or known issues that can help in troubleshooting

  14. 14. 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 transmission control systems and can perform more advanced diagnostics. By following these steps, you should be able to identify and resolve the communication error associated with the U1748 code