the yellow or pink (it can be either one of these) wire isnt connected. this is the memory wire and needs to be connected to the battery. it needs power at all times from the battery. the red wire needs to be connected to the ignition switch +ve
thus even after u turn ur switch to the off position, the red wire will stop getting current and the pre will close. but the yellow wire wire still be getting the current and will store the memory. that is, ur songs will play from the last time, source is the same when pre turns on, cd dsnt eject etc
check ur wiring. it will be this problem.