how much does it cost to replace knock sensor

I had both of mine replaced by a garage in Ft. Walton beach, Fl. in 2010 while on vacation. the cost was $500 of which, approximately $350 was labor. If I had been home, I would have replaced them myself. The Chevy dealership and the "older" salesman at Auto Zone advised me not to wait because I was risking severe detonation and head damage without knock sensors working properly. They are located under the intake manifold and require it's removal. Good luck!!

I had both of mine replaced and I was charged 386.89 and that was supposed to be a deal. You an buy the knock sensors for 39 a piece on Walmart.com and the Manifold gaskets are about 60 so if you can do it yourself