U1727 – Transmission Control Module Communication Error
The ODBII code U1727 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 U1727 is moderate to severe.
Common Causes For: U1726 U1726: CAN Communication Fault Detected
- Faulty Transmission Control Module (TCM)
- Damaged wiring or connectors
- Poor ground connections
- Faulty Engine Control Module (ECM)
- Communication network issues (CAN bus problems)
- Corroded or loose connectors
- Software issues or bugs in the TCM or ECM
- Low battery voltage or electrical issues
- Faulty sensors affecting transmission operation
- Aftermarket modifications affecting communication systems
Common misdiagnosis for U1727 U1727: 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- Software issues or outdated firmware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 in the vehicle’s communication network
Common Troubleshooting Steps
The OBD-II code U1727 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 related to 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. If possible, test the TCM by swapping it with a known good unit or using a diagnostic tool to perform a functional test.
- Inspect the CAN Bus:
- The TCM communicates with other modules via the Controller Area Network (CAN) bus. Check for any issues with the CAN bus wiring, such as shorts or opens.
- Use a scan tool to monitor the CAN bus for communication errors or interruptions.
- Check for Software Updates:
- Sometimes, a software update for the TCM or other control modules can resolve communication issues. Check with the manufacturer for any available updates.
- 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.
- Consult Service Manual:
- Refer to the vehicle’s service manual for specific diagnostic procedures and wiring diagrams related to the TCM and communication systems.
- Seek Professional Help:
- If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or technician who has experience with transmission control systems and advanced diagnostic tools. By following these steps, you should be able to identify and resolve the communication error associated with the U1727 code.