Microsoft is tightening driver security. As of 2025, many old Mini VCI drivers fail to install on Windows 11 24H2 due to the "Windows Defender Application Control" (WDAC).
Solutions for Windows 11:
If you have spent two hours fighting the yellow exclamation mark: mini vci j2534 drivers
Navigate to C:\Program Files (x86)\Toyota Diagnostics\MVCI or C:\MVCI.
Open MVCI.ini in Notepad as Administrator.
Find the section [DEVICE]. Modify it to match your COM port: Microsoft is tightening driver security
[DEVICE]
CONNECTION = COM5
BAUDRATE = 38400
TIMEOUT = 1000
Save the file. Pro tip: Set the file to "Read Only" after editing so Techstream doesn't overwrite it. Save the file
Once the drivers are working, you can optimize for performance.