iPhone 3GS in Disk Mode play MP3's/Charge on USB Car Stereo?

I got a car with a Sony CDX-GT35UW Car Stereo in it and I plugged my iPhone 3GS and came up device not supported and does not charge my iPhone either.

It Plays MP3's and Charges my SanDisk MP3 Player and other flash drives and I was reading about different things and was wondering if anybody has had this issue and put it in Disk Mode and then was able to play MP3's and Charge on a USB Car Stereo that was saying "device not supported"?

Thanks

Yeah if Jailbroken there's a in Cydia there's a USB Dive App I was wondering if anyone had any experience's with a USB Port on a car stereo and this app. Will the sterio play MP3's and charge the iPhone?

Thanks