See also:

Volume control switch
Press the switch to the “+” side to increase the volume. Press the switch to the “−” side to reduce the volume. A number indicating the volume will be shown on the audio display. ...

When “CHECK DISC” is displayed
Press the eject button to unload the discs. Check that the disc is not damaged or scratched, and also check that the disc is inserted correctly. This message may appear when using some CD-RW discs ...

How to insert a CD (type A)
While the ignition switch is in the “Acc” or “ON” position, hold a disc with a finger in the center hole while gripping the edge of the disc, then insert it in to the slot (with the label side up) ...