U1109 – refers to a communication issue, specifically indicating a Lost Communication with Vehicle Control Module.

The ODBII code U1109 indicates a communication issue where the vehicle’s control module is unable to communicate with other modules, suggesting a potential fault in the wiring, connectors, or the control module itself.

The severity of ODBII code U1109 is generally considered moderate to severe, as it indicates a communication issue that can affect multiple vehicle systems.

Common Causes For: U1108 U1108: Control Module Communication Failure

• Faulty wiring or connectors
• Damaged or corroded pins in the connector
• Failed Vehicle Control Module (VCM)
• Issues with the power supply to the VCM
• Faulty or malfunctioning sensors
• Software or firmware issues in the VCM
• Interference from aftermarket devices
• Poor ground connections
• Faulty communication network (CAN bus issues)
• Low battery voltage or weak battery

Common misdiagnosis for U1109 refers to a communication issue, specifically indicating a “Lost Communication with Vehicle Control Module.

• Faulty Vehicle Control Module (VCM)
• Wiring issues or damaged connectors
• Faulty or corroded ground connections
• Issues with the power supply to the VCM
• Faulty sensors or actuators
• Problems with the OBDII port or scanner
• Software or firmware issues in the VCM
• Other communication module failures (e.g., ABS, BCM)

Common Troubleshooting Steps

When dealing with OBD-II code U1109, which indicates a “Lost Communication with Vehicle Control Module,” there are several common troubleshooting steps you can take 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. Sometimes, multiple codes can provide more context about the issue.
• Inspect the Vehicle Control Module (VCM): **Physical Inspection: Check the VCM for any visible damage, corrosion, or loose connections.
• **Connector Check: Ensure that the connectors to the VCM are secure and free of dirt or corrosion.
• Examine Wiring and Connections: Inspect the wiring harnesses related to the VCM for any signs of wear, fraying, or damage.
• Look for any loose or corroded connectors in the communication lines.
• Check Power and Ground: Verify that the VCM is receiving the proper power supply. Use a multimeter to check voltage at the VCM connector.
• Ensure that the ground connections are secure and functioning properly.
• Test Communication Lines: Use a scan tool to check if the VCM is communicating with other modules. If other modules are also not communicating, the issue may be with the communication bus (CAN bus).
• Inspect the CAN bus wiring for shorts, opens, or other issues.
• Perform a Hard Reset: Disconnect the vehicle’s battery for a few minutes to reset the system. Reconnect and see if the code reappears.
• Check for Software Updates: Sometimes, a software update for the VCM or other modules may resolve communication issues. Check with the manufacturer for any available updates.
• Inspect for Environmental Factors: Ensure that there are no environmental factors affecting the VCM, such as moisture or extreme temperatures.
• Test the VCM: If all else fails, the VCM itself may be faulty. Consider testing it with a known good module or having it professionally diagnosed.
• Consult Technical Service Bulletins (TSBs): Check for any TSBs related to your vehicle make and model that may address known issues with the VCM or communication problems.1
• Seek Professional Help: If you are unable to resolve the issue after these steps, it may be best 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 U1109 code.