U1746 – Transmission Control Module Communication Error
The ODBII code U1746 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 U1746 is moderate to severe.
Common Causes For: U1745 U1745: Transmission Control Module Communication Error
- Faulty Transmission Control Module (TCM)
- Damaged wiring or connectors
- Poor ground connections
- Faulty Engine Control Module (ECM)
- Software issues or programming errors
- Corroded terminals
- Intermittent electrical connections
- Low battery voltage or weak battery
- Faulty CAN bus communication
- Malfunctioning sensors related to transmission
Common misdiagnosis for U1746 U1746: Transmission Control Module Communication Error
- Faulty Transmission Control Module (TCM)
- Wiring issues or damaged connectors
- Faulty Engine Control Module (ECM)
- Low transmission fluid levels
- Faulty sensors (e.g., speed sensors)
- Software issues or outdated firmware
- Battery or charging system problems
- Grounding issues
- Faulty transmission solenoids
- Corrupted data communication lines
Common Troubleshooting Steps
The OBD-II code U1746 indicates a communication error between the Transmission Control Module (TCM) and other control modules in the vehicle. Here are some common troubleshooting steps to diagnose and resolve this issue:
- Check for Other Codes: Use an OBD-II scanner to check for any additional trouble codes. Sometimes, related codes can provide more context for the issue.
- Inspect Wiring and Connectors:
- Visually inspect the wiring harness and connectors associated with the TCM. Look for signs of damage, corrosion, or loose connections.
- Ensure that all connectors are securely plugged in and that there are no bent pins.
- Check Power and Ground:
- Verify that the TCM is receiving the correct voltage and ground. Use a multimeter to check the power supply and ground connections to the TCM.
- If there is no power or ground, trace the wiring back to the source to identify any breaks or shorts.
- Test the TCM:
- If the wiring and connections are intact, the TCM itself may be faulty. Testing the TCM may require specialized equipment or a professional diagnostic tool.
- In some cases, reprogramming or updating the TCM software may resolve communication issues.
- Inspect Other Modules:
- Since the TCM communicates with other modules, check for issues with those modules as well. Look for communication errors or faults in related systems (e.g., Engine Control Module, Body Control Module).
- Ensure that all modules are functioning correctly and that their connections are secure.
- Check for Interference:
- Look for any aftermarket devices or modifications that may interfere with the vehicle’s communication network. This includes alarm systems, stereo systems, or other electronic accessories.
- Perform a Network Test:
- Use a scan tool to perform a network test to see if the TCM can communicate with other modules. This can help identify if the issue is isolated to the TCM or if it affects the entire network.
- Clear Codes and Test Drive:
- After addressing any identified issues, clear the trouble codes and take the vehicle for a test drive to see if the code reappears.
- Consult Service Manual:
- Refer to the vehicle’s service manual for specific diagnostic procedures related to the TCM and communication errors. This may provide additional insights or steps tailored to your vehicle model.
- Seek Professional Help:
- If the issue persists after performing these steps, it may be best 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 can systematically identify and resolve the underlying cause of the U1746 code.