I removed a 12-volt socket in my car and replaced it with a slick USB/ 3.5mm jack that looks close to factory. I plugged the iPod cord into the USB jack and completed the install.
When I plug a USB stick into the jack, playback and lookup on the head unit work just fine. But when I plug in an iphone 4 using a factory 30-pin to USB cord, I can control everything on the phone like normal, but there is no volume. I tried this with two different iPhone 4 handsets and two different Apple brand cords. Same result. I turned the head unit volume up to 35, I made sure the iPhone volume was arou