Engine VIN writing is a critical procedure whenever the engine control module (ECM) has been replaced, reprogrammed, or reset. A mismatched or missing VIN inside the ECM can lead to diagnostic trouble codes (DTCs), communication issues, or even immobilizer mismatches. In this article, we demonstrate how to write the VIN to the ECM using the Launch X431 PAD V / PAD 5 and other Launch X-431 diagnostic tools.
Our test vehicle is a 2020 Buick GL8 ES (LuZun) with VIN LSGUL83L1LA***.
This guide is designed for professional technicians, locksmiths, and automotive workshop users who need a reliable reference for VIN programming on GM vehicles.
Vehicle & Tool Requirements
- Test vehicle: 2020 Buick GL8 ES
- VIN: LSGUL83L1LA*****
- Diagnostic equipment: Launch X-431 PAD VII, PAD V Elite, PRO5, or other X-431 series full-system diagnostic tools
- System requirement: Stable battery voltage, internet connection for online functions
- Prerequisite: Clear all ECM-related DTCs before starting VIN writing
Step 1: Select “Intelligent Diagnose”
Power on your X-431 PAD5 and enter the Intelligent Diagnose menu.
This allows the device to read the vehicle’s VIN and automatically identify model information.
Step 2: Enter the Diagnostic Menu
After the intelligent scan completes, select “Diagnosis” to access the full-system module list.
Step 3: Open ECM (Engine Control Module)
From the system list, choose ECM – Engine Control Module.
This will load the communication interface and connect to the engine ECU.
Step 4: Select “Special Functions”
Within the ECM menu, navigate to Special Functions.
This section contains adaptation, coding, and programming functions specific to each vehicle.
Step 5: Choose “Engine VIN Writing”
Locate and tap Engine Write VIN / VIN Programming.
This function allows you to write or update the VIN stored inside the ECM.
Step 6: Confirm the Warning Message
A prompt will appear:
“Please ensure that all DTCs have been cleared before starting this operation.”
Click OK to proceed.
If DTCs are still present, exit and clear the fault codes first—GM ECUs often block VIN writing when faults exist.