phone by usb to car stereo not being recognized

I've always used my Sony Xperia with mp3s on the SD card as plug & play storage, connected by USB with my car Pioneer sound system. Phone would charge, mp3 files & folders were navigable & playable.

After a factory reset of the phone it is no longer recognized by the sound system and doesn't even charge anymore!

I tried so many things, even formatted the SD card, and some 'patch' apps....

phone model no. ST18a with Android 4.0.4

Thank you for your time!