Sony CDX-GT23W Operating Instructions Manual page 16

" " or "
During reverse or fast-forward, you have reached the
beginning or the end of the disc and you cannot go any
further.
" "
The character cannot be displayed with the unit.
If these solutions do not help improve the situation,
consult your nearest Sony dealer.
If you take the unit to be repaired because of CD
playback trouble, bring the disc that was used at the
time the problem began.
16
"