There is a vacum pump (I think) mounted on the bottom of the battery tray that is part of the system. There is one electrical connector prone to corrosion from the battery and two vacum hoses also prone to have problems. It's a pain to get to. Several posts refer to moving it from under the battery all together. I would check the vacum hoses first and then keep scanning the brickboard. I managed to screw mine up while tinkering on something else. Good luck, Jim.