There is going to be a module that you pioneer harness is wired in to, that is where you r going to turn the volume down. Just grab a small flathead and turn that sucker to the desired level and u will be golden. Also just an fyi u dont just ground the parking brake wire. Do a search on this forum to find a step by step pictorial on how to do it. If you know what u r doing it will take just a few minutes to tackle.