U1728 – Transmission Control Module Communication Error

The ODBII code U1728 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 U1728 is moderate to severe.

Common Causes For: U1727 U1727: Transmission Control Module Communication Error

• Faulty Transmission Control Module (TCM)
• Damaged wiring or connectors
• Poor electrical connections
• Faulty Engine Control Module (ECM)
• Software issues or programming errors
• Corroded terminals
• Short circuits in the wiring harness
• Faulty sensors related to transmission operation
• Issues with the vehicle’s power supply or battery
• Interference from aftermarket modifications or devices

Common misdiagnosis for U1728 U1728: 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• Software issues or outdated firmware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 U1728 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. If possible, test the TCM by swapping it with a known good unit or using a diagnostic tool to check its functionality.
• Inspect CAN Bus Communication:
• 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 any irregularities in communication.
• 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 related to the TCM and communication errors. This can provide additional insights and steps tailored to your vehicle model.
• Seek Professional Help:
• If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or dealership for further diagnosis and repair. By following these troubleshooting steps, you can systematically identify and resolve the communication error associated with the U1728 code.