See also:

External audio source volume
If an external devices such as an MP3 player or an iPod is connected to the AUX socket, the device's volume may be different from the volume of the internal sound sources such as the disc play ...

Changing
WARNING Connect and disconnect the positive and negative cables in the correct sequence. ...

Replacing the battery
1. Switch off the ignition. 2. Wait at least 5 minutes after switching off the ignition before disconnecting the battery so that all information in the vehicle's electrical system can be stored ...