Just one bolt holds it down to the engine block, and a simple two wire harness connects it. This thing was mounted under the intake manifold of my Northstar engine, so I figured that while I was in there replacing the starter, it would also make sense to install a fresh knock sensor, though nothing seemed wrong with the old one. Replacing it is just cheap insurance, considering how little it costs and the fact that this is the part that lets the engine run on regular gas without the engine knocking.