What is a knock sensor?

My error codes are for a knock sensor, a front right heated 02 sensor and a engine coolant sensor.

How do I change these and where can I buy them?

One more thing... I was about to change my tire and the lug wrench that came with the car doesnt fit the lugs. Even the smallest one doesnt fit. Its a 95 maxima with alloy factory rims. The lugs look small and I dont see 5 sides like a normal lug. Am I sounding crazy?

First a code does not say change the sensor. It says check it out.
A Knock sensor picks up engine ping or knock.
Being unpluged or bad wire is a big problem with them also a coolant senser may be unpluged..
Post back you code no for more help.
MT

I got a 01 03 and 09 08 for the engine coolant temp sensor. I got a 03 04 for the knock sensor.

Code 13 and 98 are coolant sensor or citcuit codes.
Code 34 is a knock sensor or circuit code.
Clear codes and see if they return.
MT

Code 13 and 98 are coolant sensor or citcuit codes.
Code 34 is a knock sensor or circuit code.
Clear codes and see if they return.
Are the sensors pluged on good?
Check voltage on knock sensor wire and ohms on coolant sensor or sensors.
MT

Ok. Ill do that and see what happens. Do u know where the coolant temp sensor is so i can check it?

Do know about the lug nuts? I cant get the wheel off.

...I cant get the wheel off.

- passenger side. You have not yet read the links given, see below. ALL info sits there, 'Favorite links'... waiting. go cli clic clic...
- maybe you have lock nuts? Got to get special socket; hop to a wheel shop....

Both Coolant Temp sensors located around [Ts.], here VGE
http://www.cardomain.com/ride/748507/8
http://memimage.cardomain.net/member_images/4/web/748000-748999/748507_457.jpg

I still got these codes. Im gonna chage the temp sensor first. Does the 95 have 2 or 1?

as far as your lug nuts , sounds like you have wheel locks