So, my fiance has a 1997 Neon, two door. To the left of the driver, near the fuse panel, is a little thing. (I'm not sure what to call it. It looks like a headphone jack) On the keyring is a small device that has what looks like a 3.5mm audio jack on it, and the car will not start without this inserted.
The problem is, she lost her keys, and now, despite having extra car keys, we can't start the car, because we don't have the little jack thing.
Does anyone know what this is, and where I can get a replacement?

 

its not factory so unless u take out yourself or have some one do it or find out what system it is your stuck.