Mitsubishi Repair: sterieo, player mechanism, focus error

Question
Hi                                                           My name is Amanda I have a 2004 eclipse and my radio wont play cd's it has a e03 but i don't have the cd changer its just the head unit  

Answer
Amanda,
Here are the listing as to what the error codes refer to:

E01 - Focus Error - Disc is not loaded correctly, or condensation on disc
E02 - Disc Error - Disc is dirty, scratched, or deformed; or excessive vehicle vibration
E03 - Mechanism error - Loading or eject error. Pickup-up is out of position.

The E03 error typically occurs when the CD player mechanism is damaged.  Try different types of CDs; a new music CD would be the best to try.  If that also gives the same E03 error, your CD player probably needs to be replaced.  Depending on your mileage, this may be covered under your existing warranty.  
Good luck!