Volume to max when connected to car

Hello and welcome to Apple Support Communities, thurwingwethil.

If we understand your post correctly, your iPhone is at maximum volume when connected to your car stereo via USB cable. We’d like to help.

Since your stereo uses a USB connection, please follow these steps, including checking with the manufacturer for updates for your stereo:

1. Restart your device and your car.
2. Make sure that your device is unlocked and on the Home screen.
3. If possible, try to connect using another cable or USB port. Check the manual that came with your car to learn how to connect an Apple device.
4. Check your charging port for any debris or damage. Make sure that your charging cable is properly inserted into the port.
5. Update your device.
6. Make sure that your stereo is using the latest firmware from the car manufacturer. Check your car's manual for more information.
7. Try playing audio from a different app. If you can't play audio from a third-party app, contact the app developer for help. If you can't play audio from an Apple app, contact Apple Support.

How to connect your iPhone, iPad, or iPod touch to your car

Let us know if that resolves this issue for you.

Thanks for using the Apple Support Communities.

None of your suggestions fix the problem. I was able to adjust the volume until the 15.4.1 update, and now no matter I do the volume is all the way up and cannot be changed.