Audio Systems: 2004 gmc check cd error, gmc sierra, cotton swab

Question
Hey i have a 2004 gmc sierra with a 6 disc cd player, everytime i put a cd in it ejects it back out and says "check cd". Have any suggestions

Answer
This means that the CD is not readable.  Normally this means that the CD lens is dirty.  Remove the unit and open it up.  Clean the lens using a cotton swab and alcohol.  If that does not resolve the problem, tehn either the optics are bad or the loading belt is slipping not allowing the mechanism to complete the loading cycle.
Dan