I just tried my iPod mini with the 3.5 mm audio cable and there is major hissing like you can't even hear the music. All the songs on my iPod are high audio quality. When I plug it in my Lexus via the same cable no issues. Can the dealer fix it?
Anywhere they sell audio stuff--Radio Shack would sell them. Cheaper cables are unshielded, and often times this causes interference from the car's electrical system. FWIW, monoprice.com is a great source for high quality cables, etc. at very reasonable prices--here's a 3 foot shielded cable, for ~$5 (including shipping): For only $1.41 each when QTY 50+ purchased - 3ft Premium 3.5mm Stereo Male to 3.5mm Stereo Male 22AWG Cable (Gold Plated) - Black | Premium 3.5mm Audio Male to Male Cables