Here's some generic methods to try (copied from another forum)
Precautions:
These tricks are focused mainly on single disc CD players but they may work on your multi-disk changer. Usual disclaimers - attempting repairs can ruin your player. If your car is under warranty, take it to the dealer. If you have any qualms about trying any of these techniques, let a dealer or audio shop tackle the project instead.
Tips and Tricks:
Figure out what fuse controls the CD player and, with no key in the ignition, pull the fuse out for a minute (or more - I've seen TSBs that say leave the fuse out for 10 minutes), then replace it (theory being that the fuse acts as a reset button). If you cannot find the fuse, you can disconnect the negative battery cable, but you'll lose your radio presets and other settings. Make sure you have any codes for your radio that may be required since disconnecting the battery cables can cause the radio to quit working too. This fuse trick seems to have the greatest chance of success overall. Check your owner's manual - you may have more than one fuse that controls the CD and/or the radio and you may need to remove all the related fuses.
Turn your ignition on to the accessory position. Hold the eject button down for 2 or 3 minutes. Depending on your make/model, the eject button may flash. When the button stops flashing (or when a few minutes has passed), release the button and immediately press it again (theory being that the two minutes of "work" followed by a quick break will fool the player into releasing the disc when you press the eject button again). One commenter below had success by pressing both the power button and the eject button..
At least one forum member had success releasing a stuck CD by, ahem, banging on top of the dashboard! New from the comments below - pound on the dash while pressing the button. Several people have had success with this trick so I've moved up higher in the list of things to try..
Try using some tweezers, needle nose pliers or hemostats (every tool kit needs a hemostat or two!) to pull the CD out while pressing the eject button with power going to the player (theory being that the disc is so slick the player can't eject it without help). Some people report success just by pulling the disc out with the tweezers without power to the player and without pressing the eject button..
If your player has a small hole in the front of it, like most personal computer CD players do, straighten a paperclip and push the clip straight into the hole to manually release the catch. Some players have a groove under the CD door instead of a hole. Look for a hole about the size of the paperclip and don't mistake an emergency release hole for an earphone jack..
Some players, especially aftermarket ones, use a CD cartridge or magazine. Tapping on the cartridge while pressing the eject button sometimes ejects stuck discs. Forum member Alwaysfords2 has been able to remove stuck CD magazines by using a piece of shim stock or a hack saw blade and going alongside one of the long sides of the magazine to hit the release. You can rock the magazine a little bit in the slot to see the mechanism and it should be easy to release - sort of like using the little pin hole on a CD drive, the magazine pops up as soon as it is freed..
Remove the faceplace from your player (be gentle; something like a butter knife often works without damaging the bezel or breaking tabs). Then look for a tiny, usually recessed little button that you can press. You may need that unbent paperclip to reach the button..
Find a coaster in your junk drawer - by coaster, I mean an old CD that doesn't work. Or use a blank one if that's all you have. Insert the coaster about an inch into the slot (yes, on top of the stuck CD). Then turn the ignition on and hold the eject button and wiggle the CD around. Don't be hamfisted - you're just trying to give the player some traction to help it eject the stuck one. If this fails, then try slipping the edge of the coaster (or something even thinner) under the stuck CD and pry it up while pressing the eject button. Again, be gentle - you don't want to ruin the player when a pro may be able to remove the unit and free the disc for $20 or so. One forum member has good luck with this technique using a credit card (thanks, Korber!). And another reader reports that he successfully used a credit card under the stuck CD, with just a slight upward, forward ‘lift’ to increase the eject roller pressure. Usually takes 2-3 quick actions. (thanks Roland!).
Find a Popsicle stick or something thin but rigid and tear off a few inches of Scotch Tape from that roll you keep in your junk drawer (next to all those ruined CDs you intend to make Christmas ornaments out of some day). Put the tape on the top of the stuck CD using the thin stick to help attach the tape firmly to the disk. Like the hint above, the idea is to lift the CD enough to enable the player to eject it. Here's a new variation, courtesy of forum member Glasslight. Get a thin cardboard flat rate envelope like those used for express and priority mail. Cut off the portion of the envelope with the adhesive and discard the rest. Double it over with the adhesive strips facing outward, remove the protective strips from the adhesive and inserted the strip into the CD slot. It'll grab the cd and let you pull it out of the mechanism..
Foreign objects stuck into the player, or CDs that miss the slot entirely yet wind up inside the unit usually require pulling the CD player to remove the disc..
