U2117 – Lost Communication with the Transmission Control Module (TCM).

The ODBII code U2117 indicates that there is a loss of communication between the vehicle’s onboard computer and the Transmission Control Module (TCM), which may affect the transmission’s performance and functionality.

The severity of ODBII code U2117 is typically considered moderate to severe.

Common Causes For: U2116 Lost Communication with Vehicle Dynamics Control Module.

• Faulty Transmission Control Module (TCM)
• Damaged wiring or connectors
• Poor electrical connections
• Faulty Engine Control Module (ECM)
• Blown fuses
• Corroded terminals
• Software issues or updates needed
• Low battery voltage or weak battery
• Transmission fluid issues
• Faulty CAN bus communication

Common misdiagnosis for U2117 Lost Communication with the Transmission Control Module (TCM).

• 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)
• Corrupted software or firmware in the TCM
• Battery or charging system issues
• Grounding problems
• Faulty transmission solenoids
• Issues with the vehicle’s CAN bus system

Common Troubleshooting Steps

When dealing with the OBD-II code U2117, which indicates “Lost Communication with the Transmission Control Module (TCM),” there are several common troubleshooting steps you can follow to diagnose and potentially resolve the issue. Here’s a structured approach:

• 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 affecting the TCM.
• Inspect Wiring and Connectors: **Visual Inspection: Check the wiring harness and connectors leading to the TCM for any signs of damage, corrosion, or loose connections.
• **Connector Pins: Ensure that the pins in the connectors are not bent, corroded, or pushed back.
• Check Power and Ground: **Power Supply: Verify that the TCM is receiving the correct voltage. Use a multimeter to check the power supply to the TCM.
• **Ground Connections: Ensure that the ground connections for the TCM are secure and free of corrosion.
• Inspect the TCM: **Physical Condition: Check the TCM for any signs of physical damage or water intrusion.
• **Re-seat the TCM: If applicable, disconnect and reconnect the TCM to ensure a good connection.
• Check for Communication Issues: **CAN Bus Communication: Since the TCM communicates over the CAN bus, check for issues with the CAN network. Look for any shorts or opens in the wiring.
• **Scan Other Modules: Use a scan tool to check if other modules (like the Engine Control Module) can communicate properly. If other modules are also having communication issues, it may indicate a problem with the CAN bus.
• Test the TCM: If possible, test the TCM in another vehicle of the same make and model to determine if the module itself is faulty.
• Alternatively, consider replacing the TCM if all other checks are inconclusive.
• Check for Software Updates: Sometimes, manufacturers release software updates for the TCM. Check with the dealership or manufacturer to see if there are any updates available that could resolve communication issues.
• Clear Codes and Test Drive: After performing the above checks and repairs, clear the codes using the OBD-II scanner and take the vehicle for a test drive to see if the code returns.
• Consult a Professional: If the issue persists after all troubleshooting steps, it may be necessary to consult a professional mechanic or technician who has experience with transmission control systems.Conclusion Troubleshooting a U2117 code involves a systematic approach to check for wiring issues, power supply, communication integrity, and the condition of the TCM itself. Following these steps can help identify the root cause of the communication loss with the TCM.