Auto-connect to car BT Audio Pioneer FH-P8000BT problem iPhone

When I go through the menus & pair everything, BT audio and phone pairing works flawlessly. Everything (obviously) disconnects when I turn the truck off. When turning it back on, the phone automatically re-connects every time. However, the audio feature will NOT. Even if I manually go the the BT Audio input on the radio, it doesnt work. A blinking icon pops up on the Pioneer showing that it is searching for the BT device, but it never re-connects. Go back through all the menus again (on both devices) & it comes back. Its only a problem on the BT audio. Phone works fine.
Any ideas? FYI, Ive tried multiple iterations of completely forgetting and re-learning from scratch the device on both the Pioneer and iPhone end, with full reboots in between. No dice. Im about to pull my hair out!!
iPhone 4 iOS 4