parking sensor

I am new to the Forum but I did try searching everywhere for the answer so please forgive me if it is somewhere already and I missed it. I have a 99 Limited that has every option available minus the Reversing Sensor System (Parking Aid) and from my research it appears that the wiring is already...

I was wondering if the volume of the backup seneor on my 2002 Ford Explorer Limited could be increased. Sometimes I can't hear it, especially with the radio, a/c, and outisde noise. I read somewhere that a dealership could do it, but i don't wantto pay big $$$ for such a little adjustment...