U1129 – Lost Communication with Vehicle Dynamics Control Module.

The ODBII code U1129 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 U1129 is generally considered moderate to severe.

Common Causes For: U1128 SCP (J1850) Invalid or Missing Data for Primary Id

• Faulty Vehicle Dynamics Control Module (VDCM)
• Damaged wiring or connectors
• Poor electrical connections
• Faulty or corroded ground connections
• Malfunctioning CAN bus communication
• Software issues or firmware corruption
• Other related module failures
• Battery or power supply issues

Common misdiagnosis for U1129 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 body control module (BCM)

Common Troubleshooting Steps

When you encounter the OBD-II code U1129, which indicates “Lost Communication with Vehicle Dynamics Control Module,” it typically points to a communication issue between the Engine Control Module (ECM) and the Vehicle Dynamics Control Module (VDCM). Here are some common troubleshooting steps to help diagnose and resolve the issue:

• Check for Other Codes: Use an OBD-II scanner to check for any additional trouble codes. Other codes may provide more context or indicate related issues.
• Inspect Wiring and Connectors: **Visual Inspection: Check the wiring harness and connectors related to the Vehicle Dynamics Control Module 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: Verify that the Vehicle Dynamics Control Module is receiving proper power and ground. Use a multimeter to check voltage at the module’s power supply pins.
• Check the ground connections to ensure they are secure and free of corrosion.
• Test the Vehicle Dynamics Control Module: If possible, perform a functional test of the Vehicle Dynamics Control Module. This may require specialized diagnostic equipment.
• If the module is suspected to be faulty, consider replacing it or testing it in another vehicle if available.
• Inspect the CAN Bus: The communication between modules typically occurs over the Controller Area Network (CAN) bus. Check for any issues with the CAN bus wiring, such as shorts or opens.
• Use a CAN bus scanner to monitor communication between modules and identify any anomalies.
• Check for Software Updates: Sometimes, communication issues can be resolved with a software update. Check with the manufacturer for any available updates for the ECM or VDCM.
• 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): Look for any TSBs related to the U1129 code or the Vehicle Dynamics Control Module for your specific make and model. Manufacturers may have specific recommendations or known issues.
• Seek Professional Help: If the issue persists after performing the above steps, it may be necessary to consult a professional mechanic or dealership for further diagnosis. They may have access to advanced diagnostic tools and resources. By following these troubleshooting steps, you should be able to identify and resolve the issue related to the U1129 code.