U1748 – Transmission Control Module Communication Error
The ODBII 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.
The severity of ODBII code U1748 is moderate to severe.
Common Causes For: U1747 U1747: Transmission Control Module Communication Error
- 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 misdiagnosis for U1748 U1748: Transmission Control Module Communication Error
- 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- Software issues or outdated firmware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
Common Troubleshooting Steps
The OBD-II code U1748 indicates a communication error between the Transmission Control Module (TCM) and other modules in the vehicle’s network. Here are some common troubleshooting steps to diagnose and resolve this issue:
- 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.
- 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.
- **Repair or Replace: If any damaged wires or connectors are found, repair or replace them as necessary.
- 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.
- **Ground Connections: Verify that the ground connections for the TCM are secure and free of corrosion.
- 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.
- **Termination Resistors: Ensure that the CAN bus has the proper termination resistors in place.
- 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.
- Test the TCM: **Bench Test: If possible, remove the TCM and perform a bench test to ensure it is functioning correctly.
- **Replacement: If the TCM is found to be faulty, consider replacing it.
- 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.
- 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.
- 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.
- 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.