A Mazda 3's CD player can include a CD changer. The disc player can handle MP3 files with an MP3 extension. Some Mazda 3 models can be equipped with a Bose sound system which has AudioPilot that adjusts noise levels depending on noise inside the car, and Centerpoint. Centerpoint creates 5.1 surround sound in the car. Both these Bose features can be problematic. Other issues can be related to condensation, and disc format incompatibility. These kinds of problems can be corrected by following some troubleshooting steps.
Turn Bose AudioPilot off if the volume levels fluctuate and you find it distracting. From the menu look for the "AudioPLT" selection and turn the control knob to the left to turn it off. Centerpoint is the setting below AudioPilot and is marked "CENTERPT." Turn it off using the same procedure if you are listening to MP3 files on CD's encoded with high compression and audio quality degrades. Centerpoint is only designed for two-channel stereo CD's.
Don't use the CD player if CD player components or the CD itself become clouded due to condensation. Condensation can occur when you turn the Mazda 3 heater on when the car is cold. The CD will eject as a safety measure. Try wiping it with a soft cloth to remove the clouding. Reinsert and if it ejects again, the optical parts on the CD player have condensation as well. Mazda recommends waiting up to an hour before trying the player again.
Insert compatible discs only if you continue to run into problems. The player accepts normal-sized discs only. Don't try irregular shaped discs. Self-recorded discs can be played if they were recorded using ISO 9660 level 1, ISO 9660 level 2, Joliet extended format, and Romeo extended format.
Run a ballpoint pen barrel around the outside rim of new discs if they won't play or get jammed. Sharp points and uneven, rough edges can cause the disc not to seat properly.