U1793 – refers to a communication issue between the engine control module (ECM) and the transmission control module (TCM).

The ODBII code U1793 indicates a communication issue between the engine control module (ECM) and the transmission control module (TCM), suggesting a failure in data exchange between these two components.

The severity of ODBII code U1793 is typically considered moderate to high.

Common Causes For: U1792 U1792: “Control Module Communication Failure”

• Faulty wiring or connectors between ECM and TCM
• Failed ECM or TCM
• Corrupted software or firmware in ECM or TCM
• Poor ground connections
• Short circuits or open circuits in the communication lines
• Interference from other electronic components
• Low battery voltage or weak battery
• Faulty CAN bus communication system

Common misdiagnosis for U1793 refers to a communication issue between the engine control module (ECM) and the transmission control module (TCM).

• Faulty ECM
• Faulty TCM
• Wiring issues or shorts
• Corroded connectors
• Faulty sensors (e.g., speed sensors)
• Software issues or updates needed
• Battery or charging system problems
• Transmission fluid issues
• Grounding problems
• Other communication errors in the vehicle’s network

Common Troubleshooting Steps

When dealing with OBD-II code U1793, which indicates a communication issue between the Engine Control Module (ECM) and the Transmission Control Module (TCM), there are several common troubleshooting steps you can follow:

• Check for Other Codes: Start by scanning the vehicle for any other diagnostic trouble codes (DTCs). Sometimes, related codes can provide additional context for the issue.
• Inspect Wiring and Connectors:
• Visually inspect the wiring harness and connectors between the ECM and TCM 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 Power and Ground:
• Verify that the ECM and TCM are receiving the proper power supply and ground. Use a multimeter to check voltage and ground continuity.
• Look for blown fuses that may affect the communication circuit.
• Test Communication Lines:
• Use a scan tool to check if the ECM and TCM can communicate with each other. If one module is not responding, it may indicate a fault in that module or the communication line.
• Check for short circuits or open circuits in the communication lines (CAN bus).
• Inspect for Interference:
• Look for any aftermarket devices or modifications that may interfere with the communication between the ECM and TCM.
• Ensure that there are no electromagnetic interference sources nearby.
• Update Software/Firmware:
• Check if there are any available software updates for the ECM or TCM. Sometimes, manufacturers release updates to fix communication issues.
• Perform a Hard Reset:
• Disconnect the battery for a few minutes to reset the ECM and TCM. Reconnect and see if the code reappears.
• Check for Module Failure:
• If all else fails, consider the possibility of a faulty ECM or TCM. Testing or replacing the module may be necessary.
• Consult Technical Service Bulletins (TSBs):
• Look for any TSBs related to U1793 for your specific vehicle make and model. Manufacturers may have documented common issues and fixes.
• Professional Diagnosis:
• If you are unable to resolve the issue, it may be best to consult 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 U1793 code.