U2118 – Lost Communication with the Transmission Control Module (TCM) – Bus Off.

The ODBII code U2118 indicates that there is a communication failure between the vehicle’s control modules, specifically indicating that the Transmission Control Module (TCM) is not communicating properly due to being in a “Bus Off” state, which typically means it has detected a fault and has stopped transmitting data on the communication bus.

The severity of ODBII code U2118 is typically considered moderate to severe.

Common Causes For: U2117 Lost Communication with the Transmission Control Module (TCM).

• Faulty Transmission Control Module (TCM)
• Damaged or corroded wiring or connectors
• Faulty Engine Control Module (ECM)
• Communication bus issues (CAN bus problems)
• Power supply issues to the TCM
• Faulty sensors affecting transmission operation
• Software issues or programming errors
• Short circuits or open circuits in the wiring harness
• Grounding issues in the electrical system
• Interference from aftermarket devices or modifications

Common misdiagnosis for U2118 Lost Communication with the Transmission Control Module (TCM) – Bus Off.

• Faulty Transmission Control Module (TCM)
• Wiring issues or damaged connectors
• Faulty Engine Control Module (ECM)
• Bad ground connections
• Faulty CAN bus communication lines
• Battery or power supply issues
• Faulty sensors related to transmission
• Software or firmware issues in the TCM or ECM
• Incorrectly installed aftermarket components
• Issues with the vehicle’s diagnostic tool or scanner

Common Troubleshooting Steps

When dealing with the OBD-II code U2118, which indicates “Lost Communication with the Transmission Control Module (TCM) – Bus Off,” 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 trouble codes that may be present. Codes related to the TCM or other modules can provide additional context.
• Inspect Wiring and Connectors: **Visual Inspection: Check the wiring harness and connectors related to the TCM for any signs of damage, corrosion, or loose connections.
• **Connector Pins: Ensure that the pins in the connectors are not bent or corroded.
• Check Power and Ground: Verify that the TCM is receiving the proper power supply and ground. Use a multimeter to check voltage at the TCM connector.
• Check the vehicle’s fuse box for any blown fuses related to the transmission or TCM.
• Inspect the CAN Bus: Since U2118 is related to communication issues, inspect the Controller Area Network (CAN) bus wiring for shorts, opens, or damage.
• Use a scan tool to monitor the CAN bus for proper communication between modules.
• Test the TCM: If possible, test the TCM itself. This may involve using a specialized scan tool or diagnostic equipment to check the TCM’s functionality.
• If the TCM is suspected to be faulty, consider replacing it or reprogramming it if necessary.
• Check for Software Updates: Check if there are any software updates available for the vehicle’s ECU or TCM. Sometimes, manufacturers release updates to fix communication issues.
• Inspect for Environmental Factors: Look for any environmental factors that could affect the TCM, such as moisture or extreme temperatures.
• 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 Technical Service Bulletins (TSBs): Check for any TSBs related to the specific make and model of the vehicle. Manufacturers may have documented common issues and fixes for U2118.
• Seek Professional Help: If the issue persists after performing the above steps, it may be necessary to consult a professional mechanic or dealership for further diagnosis. By following these steps, you can systematically identify and address the root cause of the U2118 code.