[CompanyXB]

So I upgraded my Iphone 3GS to OS 4.0 yesterday and can no longer control my Iphone from my head unit, always says reading file, then connection error or device error. My Iphone also says this accessory is not optimized to work with this Iphone. The work around I have found is that if you do manage to get it to start playing music, immediately go into your head units settings, and change your ipod direct control to On. Granted you lose all capabilities of controlling your music from the car controls, but hey, you can still listen to your music! If anyone has found a solution besides reverting back to the previous OS, please share the wealth.

 

[LenrdZelig]

I have an iPod Touch 2nd Gen that I upgraded to iOS 4. When I initially plugged it into my car it had reset all the controls as well as the EQ and all, but I was able to switch them back to how I had it before. I was able to get it to work in my Scion so far..... FWIW.

 

[Arstechnica]

So I upgraded my Iphone 3GS to OS 4.0 yesterday and can no longer control my Iphone from my head unit, always says reading file, then connection error or device error. My Iphone also says this accessory is not optimized to work with this Iphone. The work around I have found is that if you do manage to get it to start playing music, immediately go into your head units settings, and change your ipod direct control to On. Granted you lose all capabilities of controlling your music from the car controls, but hey, you can still listen to your music! If anyone has found a solution besides reverting back to the previous OS, please share the wealth.

Do what I did, that iphone update was also a firmware upgrade as well. Turn your iphone off (hold the top button until you get the red slider confirming Turn Off). Then hook it up, turn on your iphone (it my turn on by itself), then press the iPod button, should be gold after that!!!! The reason behind turning your iPhone off is the firmware was changed and your iphone and your car stereo have to be reintroduced to each other. I updated my phone last night and got up the next morning expecting the usual music list to work and was denied. I figured it out when I finally got to work, was kinda pissed but at least it still works.