Some firmware updates do not touch the MCU. If your steering wheel controls stop working, download the latest MCU file (mcu.bin) and flash it via the same USB method under Settings > MCU Update.
Do not download random firmware from the internet. Android Auto Firmware Latest Update 8227l
The 8227L platform is used by dozens of different manufacturers. Even if two head units look identical on the outside, the internal LCD panels, CAN-Bus decoders (for steering wheel controls), and amplifier chips may differ. Some firmware updates do not touch the MCU
Installing the wrong firmware will "brick" your device (turn it into a paperweight). Do not download random firmware from the internet
The most recent firmware updates (often rolling out under version builds like k2001, mts, or klyde depending on the manufacturer) focus heavily on stability.
Once you have the correct update.zip file (between 800MB and 1.2GB), follow this precise procedure.