Try changing the knock sensor right in front of the starter in the lower part of the block , it will be screwed into the block drain, most are on the V8 GMs and check the wire that connects to it it will burn and short out on the exhaust manifold i think it is brown?or gray?. Check your plug wires bad or leaking wires will set this code and must be routed away from the sensor wire, check your repair manual. And you need to reset the computer to remove old codes , disconnect the battery for ten seconds or so, each time you change a part or repair or you will be reading the same code set the first time.