I have a 2005 e500. The factory sub in the rear deck is intermittent. Sometimes it works fine sometimes it dosent work at all. And sometimes its popping when it does work. You never know which of the 3 situations itll be each time you get in the car. Lately it hasnt worked at all, but then today it came back to life. Im probably going to replace it but wanted to make sure its not another issue before i spent the money on the sub. Any ifeas anyone?