If the "Firmware Update" button is greyed out, ensure the handbrake is firmly engaged. :
Install (available on Google Play, side-load via APK). This app scans known update servers for your chip ID. dmhz5350bt firmware update link
: Navigate to Settings > System Information > Firmware Information to see your current version. If the "Firmware Update" button is greyed out,
: Download the ZIP file to your PC, extract it, and copy the update file (usually ending in .avh ) directly to the root directory of the USB drive—do not put it inside a folder. Step-by-Step Update Guide dmhz5350bt firmware update link
Methods vary by head unit: