On the large harness that goes to the radio, I can't figure out what 5 of the wires are for. on the harness they are b3 (light tan/white), b4 (gray), b5 (black), a6 (pink), and a7 (blue).
To play an auxiliary source you'd need to fool the deck into thinking it's a separate factory accessory, like an XM radio tuner or CD changer. That's the purpose of the adapter. If you already have a stock XM tuner or CD changer, and you don't want to use it, you might be able to cut the audio signal wires and connect them to an audio cable running to your MP3 player. Then you can set the head unit for the XM tuner but you'll get the audio from your player. But if there's no factory external source equipped in the vehicle, then this isn't an option for you.
2005 Chevrolet Impala Car Stereo Radio Wiring Diagram Car Radio Constant 12v+ Wire: Orange Car Radio Switched 12v+ Wire: Yellow Car Radio Ground Wire: Black Car Radio Illumination Wire: Gray Car Stereo Dimmer Wire: N/A Car Stereo Antenna Trigger: White Car Stereo Amp Trigger Wire: N/A Car Stereo Amplifier Location: N/A Front Speakers Size: N/A Front Speakers Location: N/A Left Front Speaker Positive Wire (+): Tan Left Front Speaker Negative Wire (-): Gray Right Front Speaker Positive Wire (+): Light Green Right Front Speaker Negative Wire (-): Dark Green Rear Speakers Size: N/A Rear Speakers Location: N/A Left Rear Speaker Positive Wire (+): Brown Left Rear Speaker Negative Wire (-): Yellow Right Rear Speaker Positive Wire (+): Dark Blue
