Itunes isn't playing in my headset

Start playing and then increase volume. When you are on a different screen, volume increase or decrease doesn't apply to iTunes.

Not sure, If the manual, from the car radio says it should pair with Apple bluetooth devices, it must be a setup problem. If your radio is not (yet) compatible with MP3 over bluetooth from Apple devices, you should ask nissan if they have intentions to upgrade the software in the radio. I think you spent enough on your car, to get this kid of service.
I'm sure most modern car radio's are compatible, because my 2 year old Toyota Yaris can play my music and take my calls from my iPhone 4 without problems.

Try backing up your iphone in itunes, when you plug it in and shows up in itunes, right click on your iphone and click back up. Then after thats done, right click again and click restore, itll ask if you want to set it up as a new phone, click the option that says to restore from backup or previous iphone.

If you need further help, I’m available over the phone at https://www.6ya.com/expert/erik_3934b541f17c4e99

You can't normally take music off a iphone or ipod with itunes (is a one way street)

but try this

http://lifehacker.com/394046/copy-music-from-your-iphone-or-ipod-to-your-computer-for-free

downlaod it again

I have the same problem with my HBS-250. It was working fine on my iPod Touch. It worked the first couple of weeks on my iPhone 4 then stopped playing music. Phone funtion works. No music or podcasts or streaming from the web

Well currently, on (Non-hacked) iPhone the only way to get music on the iPhone is via iTunes, so if the song plays on iTunes, it should play on the iPhone.