U1123 – Lost Communication with Vehicle Dynamics Control Module.

The ODBII code U1123 indicates that there is 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 U1123 is generally considered moderate to severe.

Common Causes For: U1122 SCP (J1850) Invalid or Missing Data for Odometer

• Faulty Vehicle Dynamics Control Module (VDCM)
• Damaged wiring or connectors
• Corroded connectors
• Poor ground connection
• Faulty communication network (CAN bus issues)
• Malfunctioning sensors related to VDCM
• Software or firmware issues in the VDCM
• Battery or power supply issues affecting the VDCM

Common misdiagnosis for U1123 Lost Communication with Vehicle Dynamics Control Module.

• Faulty ABS module
• Wiring issues or shorts
• Faulty wheel speed sensors
• Malfunctioning engine control module (ECM)
• Incorrectly calibrated or faulty steering angle sensor
• Battery or charging system problems
• Faulty traction control system components
• Issues with the body control module (BCM)

Common Troubleshooting Steps

When dealing with the OBD-II code U1123, 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: Check the VDCM for any physical damage or signs of failure.
• **Reprogramming: If applicable, consider reprogramming or updating the software of the VDCM.
• Check for Communication Issues: **CAN Bus Integrity: Inspect the Controller Area Network (CAN) bus for continuity and proper operation. Use a scan tool to monitor the communication between modules.
• **Interference: Look for any potential sources of electrical interference that could affect communication.
• Test the VDCM: If possible, perform a functional test of the VDCM using a scan tool to see if it responds to commands and communicates with 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 manufacturer-specific TSBs related to the U1123 code or the VDCM. There may be known issues or recalls that could apply.
• Professional Diagnosis: If the issue persists after performing the above steps, consider seeking help from a professional mechanic or dealership with experience in diagnosing communication issues.Additional Tips: – Always refer to the vehicle’s service manual for specific diagnostic procedures and specifications. – Ensure that the vehicle’s battery is in good condition, as low voltage can cause communication issues. By following these steps, you should be able to identify the root cause of the U1123 code and take appropriate action to resolve it.