ubuntu phone E5: bluetooth doesn't connect to headset

Try to connect to my ubuntu-phone with my car speakerphone. It doesn't connect.
This is what going on:
Start connection; ask for coupling code; put in and confirm; ubuntu-phone connect to the speakerphone with headset mode.
Everything seams to be good, but the car speakerphone is still wating for something.
After one Minute the car speakerphone disconnect with no confirmation message.
What can I do?