The E04 error message may occur when the laser for the CD player is unable to read the disc being played. Follow this procedure to troubleshoot why the disc will not play:
- There are many car CD players that are not designed to play CDR or CDRW discs. Check the user manual that came supplied with your unit for disc compatibility.
- If model-specific information is needed to complete any of these steps, refer to the instructions supplied with the product. Manuals are posted on your model support page.
NOTE: Because each of these steps represents a possible solution to this issue, check the CD player status after completing each step.
- Play different discs to see if the issue occurs with all CDs or just a few.
NOTE: If the issue only occurs with a few CDs, then the issue may be with those discs.
- Examine the CD for any fingerprints or smudges, and clean if necessary.
- Check all wires to verify a good connection.
- Perform a reset on the car stereo.
NOTE: The laser pick up may be dirty and need to be cleaned. Sony does not recommend the use of an over-the-counter CD/DVD player lens cleaner. These lenses should be cleaned by a factory-trained Sony technician only.
The troubleshooting steps listed above should resolve your issue. If you have completed all of the steps and the issue is not resolved, service may be required.  Go to Product Repair.