I have a 2011 Subaru Impreza and bought an iPhone 6 last October. It paired to my car radio just fine until iOS 8.3 came out.
Now, I can get the car to pair to the phone IF I try several times to connect. I have to turn off the radio and turn it on again after pressing the car device. If I do this several times the phone eventually connects. I'm not sure what eventually gets it to connect, the only thing that I know is that I have to keep turning the radio on and off and re-trying the pairing from the phone, and eventually it pairs, sometimes even when the radio is off.
When I recently took the car to the dealer, I asked if they had a fix for it or if I needed to wait for Apple to fix it. He told me that many people are having this issue with the iPhones and pairing. So, while you may not have the problem, it does exist.
I have tried resetting the network settings and resetting all settings then re-pairing the phone. Never works. I have also been on Apple phone support and they can't help me fix the problem.
My son who is 15 will start driving and we have been planning on him getting this car. However, I'm not going to have a teenager drive a car that doesn't have handsfree phone working at a higher reliability than this one works. Not sure what we'll do, but am hoping that Apple will come out with a fix for those of us who aren't able to simply buy a new car.
The iphone DOES pair with my husband's 2015 Subaru Outback, so there's something in the older software that is causing the problem.