like i said i dont usually mess with egr valves but there usually connected to the exhaust with small metal tube/s coming off the exhaust manifold and go to the egr valve, if it has high mileage then it might just be stuck open or closed cause that check engine light to come on but i would fix the knock sensor asap before worrying about the egr cause thats just emmission crap.

 

Thanks for your help here. Car has 170K miles. Where is the knock sensor, is this just an 02 sensor? How do i replace it?

 

your knock sensor is right under your intake manifold plenum it will take according to alldata 4.2 hours