I put in a amp and a sub last weekend and connected the remote wire to the 12v supply in the front. I had my rear seats stripped out and the all the trim removed as I have a 3 door , my plan was to put speakers in as there was none as standard . However I'm missing something , more to the point while this was all of I earthed mine using a bolt that was holding some sort of bracket in place and tightened it down on that.