I have seen adapters in the $50-60 range that will allow this, but there is a catch. You must have some type of "AUX" device attached such as the CD changer for this device to work. It basically uses the serial data from the auxiliary device to allow the radio to switch to the AUX mode then allows you to toggle between the audio output from that device or from another device of your choice (i.e. MP3 player). I can probably find the link again if you're interested. It doesn't sound like your vehicle is equipped with a factory remote cassette player or CD changer, so you wouldn't be able to use this adapter. I'm not aware of an adapter that would accomplish this without having the tape deck or cd changer installed.
Roger
Is anyone familiar with the Delco radios used in the new vehicles?
> I have a standard RDS radio with Single CD. Is there a harness available
> for this radio that
> will allow an AUX input? There is a CD/AUX button on the radio, the AUX (I
> assume) was used for a internal tape player on another model radio.
> I want to add an mp3 or other player, but dont want to use an FM modulator.
> I'm hoping to go directly though the radio inputs if available.
>
> Anyone have any ideas?
> The vehicle also has Onstar which is somehow incorporated into the radio. >
>