U1125 – Lost Communication with Vehicle Dynamics Control Module.

The ODBII code U1125 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 U1125 is generally considered moderate to severe.

Common Causes For: U1124 SCP (J1850) Invalid or Missing Data for Primary Id

• Faulty Vehicle Dynamics Control Module (VDCM)
• Damaged or corroded wiring or connectors
• Poor ground connection
• Faulty communication network (CAN bus issues)
• Malfunctioning other related modules
• Software or firmware issues
• Blown fuses related to the VDCM or communication network

Common misdiagnosis for U1125 Lost Communication with Vehicle Dynamics Control Module.

• Faulty ABS module
• Wiring issues or shorts
• Faulty wheel speed sensors
• Malfunctioning engine control module (ECM)
• Incorrectly diagnosed transmission issues
• Battery or charging system problems
• Faulty powertrain control module (PCM)
• Issues with the instrument cluster
• Corrupted software or firmware in control modules
• Faulty connectors or terminals

Common Troubleshooting Steps

When dealing with the OBD-II code U1125, 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, multiple codes can provide more context about the issue.
• 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: If possible, check the condition of the VDCM itself. Look for any signs of physical damage or water intrusion.
• **Reprogramming: In some cases, the module may need to be reprogrammed or updated with the latest software.
• Check for Communication Issues: **CAN Bus Communication: Since the VDCM communicates over the CAN bus, check for any issues with the CAN network. Look for other modules that may not be communicating properly.
• **Termination Resistors: Ensure that the CAN bus termination resistors are present and functioning correctly.
• 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 diagnostic tools, perform a functional test of the VDCM to see if it responds to commands and communicates with other modules.
• Consult Technical Service Bulletins (TSBs): Check for any TSBs related to the U1125 code or the specific vehicle model. Manufacturers may have issued guidance on common issues and fixes.
• 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 make and model.
• Document Findings: Keep a record of any tests performed, findings, and repairs made. This documentation can be helpful for future reference or if you need to escalate the issue. By following these steps, you should be able to identify the root cause of the U1125 code and take appropriate action to resolve the communication issue with the Vehicle Dynamics Control Module.