HT3647: iOS: Supported Bluetooth profilesLearn about iOS: Supported Bluetooth profiles
Currently Being ModeratedDec 31, 2012 1:44 PM (in response to Momasbo)
Try unpairing the iPhone 3GS from your Cadillac, then try pairing the iPhone 5 again.
You can find more troubleshooting info in this Apple doc -> iOS: Troubleshooting car stereo connections
Also, iOS 6 uses AVRCP 1.4 so you may need to update the reciever in the car to make it compatible with with all versions of ACRCP.