U1391 – ECM Communication Malfunction

The ODBII code U1391: ECM Communication Malfunction indicates a communication issue between the Engine Control Module (ECM) and other control modules in the vehicle.

The severity of ODBII code U1391 is generally considered moderate.

Common Causes For: U1390 Lost Communication with the Body Control Module (BCM).

• Faulty Engine Control Module (ECM)
• Poor electrical connections or wiring issues
• Corroded connectors
• Faulty communication lines (CAN bus)
• Malfunctioning sensors
• Software issues or outdated firmware
• Battery or charging system problems
• Grounding issues
• Interference from aftermarket devices or modifications

Common misdiagnosis for U1391 U1391: ECM Communication Malfunction

• Faulty ECM (Engine Control Module)
• Wiring issues or damaged connectors
• Faulty sensors (e.g., crankshaft or camshaft position sensors)
• Battery or charging system problems
• Corrupted software or firmware in the ECM
• Issues with other control modules (e.g., TCM, BCM)
• Grounding issues
• Faulty communication lines (CAN bus issues)

Common Troubleshooting Steps

The OBD-II code U1391 indicates an “ECM Communication Malfunction.” This code typically suggests that there is a communication issue between the Engine Control Module (ECM) and other modules in the vehicle. Here are some common troubleshooting steps to diagnose and resolve this issue:

• Check for Additional Codes: Use an OBD-II scanner to check for any other trouble codes that may be present. Sometimes, multiple codes can provide more context for the issue.
• Inspect Wiring and Connectors: Visually inspect the wiring and connectors related to the ECM and other modules. Look for signs of damage, corrosion, or loose connections.
• Pay special attention to the ground connections, as poor grounding can lead to communication issues.
• Check Power Supply: Ensure that the ECM is receiving the proper voltage. Use a multimeter to check the power supply to the ECM and verify that it is within the manufacturer’s specifications.
• Test the ECM: If possible, test the ECM to ensure it is functioning correctly. This may involve using a scan tool to check for communication with the ECM or swapping it with a known good unit.
• Inspect Other Modules: Check other control modules in the vehicle for communication issues. If one module is malfunctioning, it can affect communication with the ECM.
• Ensure that all modules are properly connected and functioning.
• Check for Short Circuits or Open Circuits: Use a multimeter to check for short circuits or open circuits in the communication lines (CAN bus or other communication protocols) between the ECM and other modules.
• Look for Software Issues: Sometimes, a software glitch can cause communication problems. Check if there are any available software updates for the ECM or other modules.
• 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 issued guidance on common issues related to ECM communication.
• Seek Professional Help: If the issue persists after performing the above steps, it may be necessary to consult a professional mechanic or technician who has experience with the specific vehicle and its systems. By following these troubleshooting steps, you can systematically identify and resolve the underlying cause of the U1391 code.