The reasons are as follows:

1. The call volume on the mobile phone is not turned on.

2. The volume of the integrated car navigation system is not turned on. Turn it on.

3. There is no pairing connection between the car Bluetooth and the mobile phone. If it is an Android phone, the media volume on the phone may not be turned on. While playing music, press your phone's volume buttons, adjust the phone's volume, turn the media volume to maximum, and then adjust the volume in the car.

Solution:

First, turn on the car’s Bluetooth. Click Settings on the home page of your phone, then click Bluetooth. Find the car Bluetooth name, tap to pair, tap the arrow behind the Bluetooth name after pairing, and then turn on the slider behind Media Audio. Return to the mobile phone desktop and turn on music playback.

Note: Before taking the above measures, you must ensure that the device problem is eliminated. Make sure your phone's Bluetooth settings are set to visible to everyone, searchable, or turned on for detection. Also, make sure your phone’s Bluetooth function is turned on and visible.