Loading unverified firmware can "brick" your device (make it permanently unusable).
Since the menu icons are often universal (gears for settings, musical notes for audio), you can use the app to translate the screen in real-time. Open the Google Lens app on your smartphone. Point your camera at the AVN669HD screen. Eclipse Avn669hd Change Language
Check specialist forums or JDM importers like JustAnswer for advice on whether a specific English boot disc exists for the AVN669HD. Japanese Term English Meaning 設定 (Settei) Settings / Setup 言語 (Gengo) 英語 (Eigo) 日本語 (Nihongo) 戻る (Modoru) Back / Return Change Car Radio Language from Japanese to English Loading unverified firmware can "brick" your device (make