U1740 – Transmission Control Module Communication Error

The ODBII code U1740 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 U1740 is moderate to severe.

Common Causes For: U1739 U1739: “Module Communication Failure”

• Faulty Transmission Control Module (TCM)
• Damaged wiring or connectors
• Poor electrical connections
• Faulty Engine Control Module (ECM)
• Software issues or bugs
• Low battery voltage
• Corroded terminals
• Faulty CAN bus communication
• Intermittent electrical issues
• Grounding problems

Common misdiagnosis for U1740 U1740: 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• Software issues or outdated firmware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 U1740 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 for any signs of damage, corrosion, or loose connections.
• Pay special attention to the connectors at the TCM and any junction points in the wiring.
• Check Power and Ground:
• Verify that the TCM is receiving the correct power supply and ground. Use a multimeter to check voltage at the TCM connector.
• Ensure that the ground connections are clean and secure.
• Test the TCM:
• If possible, test the TCM for proper operation. This may involve using specialized diagnostic equipment or swapping in a known good TCM if available.
• 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 or connections.
• Use a scan tool to monitor the CAN bus for any irregularities or communication failures.
• Check for Software Updates:
• Sometimes, a software update for the TCM or other related modules can resolve communication issues. Check with the manufacturer for any available updates.
• Clear Codes and Test Drive:
• After performing any repairs or inspections, clear the trouble codes 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.
• Professional Diagnosis:
• If the issue persists after performing the above steps, consider seeking help from a professional mechanic or dealership with experience in diagnosing transmission control issues. By following these steps, you can systematically identify and address the root cause of the U1740 code.