I have a Pioneer DEH-P5100UB head unit with a Pioneer CD BTB-200 bluetooth adapter. I was successfully able to register my new iPhone 4S with the head unit, which allows for automatic bluetooth reconnection next time I enter the vehicle.

Following this success, I attempted to do the same for my wife's LG enV Touch phone. I was able to pair it with the Pioneer unit, and I "registered" it in the P2 slot. But somehow the registration does not hold. When I turn off the ignition in the car, it loses the connection with the phone and does not automatically reconnect.

I talked with Pioneer tech support today, and the tech acted surprised when I told him that my iPhone would reconnect automatically. I told him even my old iPhone 3Gs reconnected automatically. He said something to the effect that the unit doesn't have enough processing power to register two phones, that it would only re-register one phone automatically. I suppose I should give him the benefit of the doubt, but something about his responses made me think he was talking out his butt.

Has anybody had any luck pairing two cell phones with one head unit? I'm most interested in my particular Pioneer head unit, but curious about results with any head unit.