Set your car’s media (music) source to CarPlay, then adjust the volume while CarPlay navigation voice prompts are playing.

Steps

Make sure the navigation voice with the wrong volume is coming from your iPhone and not from MINI’s built-in navigation software. Here’s an easy way to check: tap the arrow icon () to the right of the Home button (). If the map screen that opens is square, that’s CarPlay—and that’s the volume we need to change. If it fills the entire round screen, it’s MINI’s built-in navigation.

1. Tap the music app button to the left of the Home button () at the bottom of the screen. In China, this button might be the NetEase Cloud Music icon, the QQ Music icon, and so on, and your case may differ from all these. Tap it repeatedly until a menu appears that lets you choose the audio source.
2. In that menu, tap CarPlay. It’s usually the first item in the menu—in the upper-left corner.
3. At this point, music should play through CarPlay—that is, through the music app on your phone. Now all audio sources (including navigation and music) are coming from CarPlay. You’re all set.
4. While navigation is giving voice prompts, turn the volume knob. If the volume bar shows two segments in different colors, you’ve adjusted it successfully.
5. If navigation doesn’t give any voice prompts for a while, some navigation screens (such as Amap) let you tap the map display button, which has a volume adjustment option. Once you’re on that screen, you can turn the volume knob freely to adjust the volume.