Hmmmmmmmm, I assume you tried more than once. If the radio works then the PIN is being recognized. You certain there is no CD's jammed in there (previous owner)?
From the Manual;
CD ERROR PLAY: The CD cannot be read. The CD is
dirty, scratched, wet, or upside down.
CD ERROR MECH (Mechanism): If this message
appears on the display, it could be for one of the
• The CD is stuck in the player and cannot be
played, loaded, or ejected.
• It is very hot. When the temperature returns to
normal, the CD should play.
• You are driving on a very rough road. When the
road becomes smoother, the CD should play.
• The air is very humid. If so, wait about an hour and
• There may have been a problem while burning
• The label may be caught in the CD player.
If the CD is not playing correctly, for any other reason,
try a known good CD.
If any error occurs repeatedly or if an error cannot be
corrected, contact your dealer. If the radio displays
an error message, write it down and provide it to your
dealer when reporting the problem.
Hope any portion of this helps.