U1702 – refers to a communication issue between the transmission control module (TCM) and the engine control module (ECM).

The ODBII code U1702 indicates a communication issue between the Transmission Control Module (TCM) and the Engine Control Module (ECM), suggesting a failure in data exchange or signal transmission between these two components.

The severity of ODBII code U1702 is generally considered moderate to high.

Common Causes For: U1701 CAN Communication Bus Fault.

• Faulty Transmission Control Module (TCM)
• Faulty Engine Control Module (ECM)
• Damaged or corroded wiring harness
• Poor electrical connections
• Faulty CAN bus communication
• Blown fuses
• Software issues or programming errors
• Grounding issues
• Faulty sensors related to transmission or engine
• Intermittent electrical issues

Common misdiagnosis for U1702 refers to a communication issue between the transmission control module (TCM) and the engine control module (ECM).

• Faulty Transmission Control Module (TCM)
• Faulty Engine Control Module (ECM)
• Wiring issues or damaged connectors
• Faulty sensors (e.g., speed sensors)
• Low transmission fluid levels
• Transmission solenoid issues
• Battery or charging system problems
• Grounding issues
• Software or firmware issues in the TCM or ECM
• Incorrectly installed aftermarket components or modifications

Common Troubleshooting Steps

When dealing with OBD-II code U1702, which indicates a communication issue between the Transmission Control Module (TCM) and the Engine Control Module (ECM), there are several common troubleshooting steps you can follow:

• Check for Additional Codes: Start by scanning the vehicle for any other trouble codes. Sometimes, multiple codes can provide more context for the issue.
• Inspect Wiring and Connectors:
• Visually inspect the wiring harness and connectors between the TCM and ECM for any signs of damage, corrosion, or loose connections.
• Ensure that all connectors are securely plugged in and that there are no bent pins.
• Check for Short Circuits or Open Circuits:
• Use a multimeter to check for continuity in the wiring between the TCM and ECM. Look for any shorts to ground or open circuits that could be causing communication issues.
• Inspect Ground Connections:
• Ensure that the ground connections for both the TCM and ECM are clean, tight, and free of corrosion. Poor ground connections can lead to communication problems.
• Test the TCM and ECM:
• If the wiring and connections appear to be in good condition, you may need to test the TCM and ECM for proper operation. This may involve using a scan tool to check for communication with each module.
• Check for Software Updates:
• Sometimes, communication issues can be resolved with a software update. Check with the manufacturer or a dealership to see if there are any available updates for the TCM or ECM.
• Inspect the CAN Bus:
• If your vehicle uses a Controller Area Network (CAN) for communication, check the CAN bus for any issues. This may involve checking the resistance and voltage levels on the CAN lines.
• Clear Codes and Test Drive:
• After performing the above checks and repairs, clear the trouble codes and take the vehicle for a test drive to see if the code returns.
• Consult Technical Service Bulletins (TSBs):
• Look for any TSBs related to the U1702 code for your specific vehicle make and model. Manufacturers may have specific recommendations or known issues that can help in troubleshooting.
• Professional Diagnosis:
• If you are unable to resolve the issue after these steps, it may be necessary to seek the help of a professional mechanic or technician who has experience with your vehicle’s specific systems. By following these steps, you can systematically diagnose and potentially resolve the communication issue indicated by the U1702 code.