Got a code for knock sensor that probably piggybacked p0400. Had the new sensor for a while but never really got around to fixing it. Just wanted to share how I changed mine out:
https://i.imgur.com/rtbgonl.png

Used not sure how long extension:
https://i.imgur.com/SXtZvev.jpg

With a universal swivel & 12mm 6-sided socket (Duralast swivel):
https://i.imgur.com/k0hg4EE.jpg

Took off stock air intake up until throttle body:
https://i.imgur.com/xubtUzv.jpg

From here it was pretty basic, just positioned the socket onto the bolt, carefully loosened it. Once unbolted, I carefully grabbed it by the harness and making sure the bolt did't fall out, pulled it out of the tight space. Took the bolt and set it aside, then used needle nose pliers to pull the harness off of the metal bracket. This was the easy part (about 7 mins)

Old KS didn't look so good, it cracked at the seam in the plastic:
https://i.imgur.com/dPdyD83.jpg

The hard part was getting the new knock sensor in. At first I tried to pull off the EGR vaccuum solenoid to get better access to the KS location but I had trrouble getting the bolt off the bracket. So in frustration I bent the bracket toward myself which in turn gave me enough room to stick my hand in:
https://i.imgur.com/7iGgTqt.jpg
https://i.imgur.com/1wCF1Rg.jpg

My hand is not small it is actually rather large but was still able to fit inside with the bracket pulled:
https://i.imgur.com/jmK6xlO.jpg

To get the KS in I grabbed it and positioned it near the KS location. Then grabbed the bolt and proceeded to guide it near the hole, and eventually lined it up blindly with the knock sensor and the mounting hole and screwed it in with my middle, and pointer finger, and later after rearranging my hand, tightened it with my thumb and pointer finger. Once it was mounted I tightened carefully with a ratchet.

KS installed:
https://i.imgur.com/eoWd6Ul.jpg

 

After clearing my codes, and taking a test drive, I could immediatley feel a difference. For the longest time I had alot of hesitation from the engine. I had cleaned my throttle body, iacv, stock intake, and maf to no avail. I still get a bit of hesitation but the overall perfomance at idle has smoothed out alot. Acceleration has improved enough to notice, especially in first/second gear. My mpg has been pretty bad lately and im sure it will now improve. For anybody that has a code or can visually see that it is bad I would change it.

 

It is a good idea to change both upstream sensors at the same time. The other one might not throw a code quite yet, but is tired.
You might consider installing the other sensor next time you have a chance.

 

Whoops.... I thought you were talking oxygen sensors. My bad...

Yes, the knock sensor makes quite a difference with performace. Enjoy the new found power and gas mileage. Use premium of course.

 

A bad ks doesn't cause hesitation. It just forces the ECU to use a fuel program for lower octane 87. So you don't get the cars full power

 

Ive been using premium since purchase. By the way the car was taken care of, I can tell they only used 87.

Well whatever it was, my car now idles alot better and is overall alot smoother on the low end. My gf immediatley noticed before I even said anything.