U1120 – Lost Communication with Vehicle Dynamics Control Module.

The ODBII code U1120 indicates a loss of communication between the vehicle’s control module and the Vehicle Dynamics Control Module, which may affect systems like traction control and stability control.

The severity of ODBII code U1120 is generally considered moderate to severe.

Common Causes For: U1119 SCP (J1850) Invalid or Missing Data for Primary Id

• Faulty Vehicle Dynamics Control Module (VDCM)
• Damaged wiring or connectors
• Poor electrical connections
• Blown fuses
• Malfunctioning CAN bus
• Software issues or programming errors
• Corrosion in connectors or terminals
• Faulty sensors related to vehicle dynamics
• Issues with the power supply to the VDCM

Common misdiagnosis for U1120 Lost Communication with Vehicle Dynamics Control Module.

• Faulty ABS Module
• Faulty Wheel Speed Sensors
• Wiring Issues or Short Circuits
• Faulty Engine Control Module (ECM)
• Faulty Body Control Module (BCM)
• Incorrectly Installed Aftermarket Accessories
• Battery or Charging System Issues
• Faulty Powertrain Control Module (PCM)

Common Troubleshooting Steps

When dealing with the OBD-II code U1120, which indicates “Lost Communication with Vehicle Dynamics Control Module,” there are several common troubleshooting steps you can follow to diagnose and potentially resolve the issue. Here’s a structured approach:

• Check for Other Codes: Use an OBD-II scanner to check for any additional trouble codes. Sometimes, other codes can provide context or indicate related issues.
• Inspect the Wiring and Connectors: **Visual Inspection: Check the wiring harness and connectors related to the Vehicle Dynamics Control Module (VDCM) for any signs of damage, corrosion, or loose connections.
• **Connector Pins: Ensure that the pins in the connectors are not bent, corroded, or damaged.
• Check Power and Ground: **Power Supply: Verify that the VDCM is receiving the correct voltage. Use a multimeter to check the power supply to the module.
• **Ground Connection: Ensure that the ground connection for the VDCM is secure and functioning properly.
• Inspect the Vehicle Dynamics Control Module: **Module Condition: Check the VDCM for any physical damage or signs of failure.
• **Reprogramming: If applicable, consider reprogramming or updating the module’s software, as a software glitch can sometimes cause communication issues.
• Check for Communication Issues: **CAN Bus Communication: Since the VDCM communicates over the CAN bus, check for issues with the CAN bus wiring and other modules on the bus.
• **Network Integrity: Use a scan tool to monitor the CAN bus for any irregularities or communication failures with other modules.
• Perform a Hard Reset: Disconnect the vehicle’s battery for a few minutes to reset the vehicle’s electronic systems. Reconnect and see if the code reappears.
• Test the VDCM: If you have access to a diagnostic tool that can communicate with the VDCM, perform a functional test to see if the module responds correctly.
• Check for Environmental Factors: Sometimes, environmental factors such as moisture or extreme temperatures can affect module performance. Ensure that the module is not exposed to conditions that could cause failure.
• Consult Technical Service Bulletins (TSBs): Check for any TSBs related to the specific make and model of your vehicle. Manufacturers may have issued guidance on common issues related to the VDCM.
• 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 your vehicle’s specific systems.Conclusion Troubleshooting a U1120 code involves a systematic approach to identify and rectify communication issues with the Vehicle Dynamics Control Module. Always ensure safety precautions are taken when working with vehicle electronics, and consult a professional if you are unsure about any steps.