I recently had a Pioneer DEH8400BT installed in my BMW 1 Series registered in 05.

And everything worked fine and the reverse sensors used to come in over my music so i could hear them no matter how load the stereo was, but now it seems to have stopped and the company who fited the stereo say that it should never have worked in the first place, but im 100% sure it was working they say they have tried replacing the box and wires which connects to the steering wheel and also the rear sensors.

can anyone please help how do i get the sencors to work over the stereo or through the speakers?

i do nto trust the place where i got this from and think they are now making excuses. As i know this worked before?