U1128 – Lost Communication with Vehicle Dynamics Control Module.

The ODBII code U1128 indicates that there is a loss of communication between the vehicle’s onboard computer and the Vehicle Dynamics Control Module, which may affect systems like traction control and stability control.

The severity of ODBII code U1128 is generally considered moderate to severe.

Common Causes For: U1127 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 lines (CAN bus issues)
• Malfunctioning sensors related to vehicle dynamics
• Software or firmware issues in the VDCM
• Battery or power supply issues affecting the VDCM
• Interference from aftermarket modifications or devices

Common misdiagnosis for U1128 Lost Communication with Vehicle Dynamics Control Module.

• Faulty ABS module
• Defective wheel speed sensors
• Malfunctioning engine control module (ECM)
• Wiring issues or damaged connectors
• Faulty powertrain control module (PCM)
• Incorrectly diagnosed brake system issues
• Battery or charging system problems
• Software or firmware issues in the vehicle’s control modules

Common Troubleshooting Steps

When dealing with the OBD-II code U1128, 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.
• **Scan Other Modules: Use a scan tool to check if other modules can communicate properly. If other modules are also having communication issues, it may indicate a problem with the CAN bus.
• Perform a Hard Reset: Disconnect the vehicle’s battery for a few minutes to reset the vehicle’s computer systems. Reconnect and see if the code reappears.
• Test the VDCM: If all else fails, you may need to test the VDCM itself. This may involve bench testing the module or replacing it with a known good unit to see if the problem persists.
• Consult Technical Service Bulletins (TSBs): Check for any TSBs related to the U1128 code or the specific vehicle make and model. Manufacturers may have issued guidance on common issues and fixes.
• Seek Professional Help: If you are unable to resolve the issue after these steps, it may be best to consult a professional mechanic or technician who has experience with your specific vehicle make and model.Conclusion Troubleshooting OBD-II code U1128 involves a systematic approach to check for wiring issues, module functionality, and communication integrity. Always ensure safety precautions are taken when working on vehicle electronics.