Follow the instructions below to update the Embedded Controller (EC):
Download the flash from operating system ThinkCentre M90z BIOS package 9BJY41USA.exe from Lenovo support website. NOTE: Only 9BJY41UAS, or above, BIOS contains EC version 33A.
Run 9BJY41USA.exe and extract files to a folder. The default folder is C:\SWTOOLS\FLASH\9BJY41USA.
Navigate to the folder where the files were extracted. Run the flash.cmd to update the BIOS to 9BKT41A. Using administrator privileges, run ec.cmd to flash EC firmware up to 9BCT33A. Do not power off system flashing EC firmware. The system must reboot after flashing new EC firmware.
The EC version can be checked in the BIOS setup screen. NOTE: The BIOS version and EC firmware version may not match.