i got a 97 maxima with 170k miles on them that is giving me a CEL for knock sensor error and EGR code P400......i changed the knock sensor about 3 yrs ago....do you think the knock sensor just went back within three years or is trigger by the EGR code? do you think is worth a try to get them sensor from ebay for like $30 bucks sshipped? are they any good?

 

I've read that other things may cause the KS code to come up so try to fix it all. You can get a generic KS off ebay or a real OEM one. Just be careful because some say oem but they are the cheap generic kind. The generic one will work but if you are **** about your car or afraid of problems then stick with a oem one. If the KS is bad and you don't change it then you gas mileage and power will be sucky. I stuck a resistor in mine but I had a coil pack go bad which I replaced so I know it's ok now. I don't know if that would be safe for you since you have other issues. You might need to clean your egr.

 

Fix the EGR first, then see if the KS code keeps coming back.

 

i would replace the knock sensor and check the egr.

 

Really .... why?

I think it would be beneficial for anyone considering changing the KS to read up () first. It's not going to make a difference in my opinion. I agree, fix the EGR code and see what / if anything else comes up. And, FYI the KS will not trip the CEL, it's a ghost code.

 

hmm changed my knock sensor today and it made a differance to me can tell the car def has more power than it did before, and we'll see about gas mileage this week

 

That damn knock sensor. I remember when i changed mine about 20K ago. I'm auto and i wasn't able to spin my bald *** tires. Then i changed it and i could spin my tires at like 3/4 throttle. That little sensor makes a lot of difference in our cars.

I think they need to be listed as 50K replacement for tuneups.








So... who on here has their original knock sensor in? Anyone?

 

What about cleaning your egr? People made it sound difficult but it was quite easy. I just cleaned out the egr valve which wasn't that dirty and sprayed lots of carburetor cleaner down the metal tube and no more code.

 

to propperly clean the EGR, you need to remove the UIM and EGR tube. Not hard ... just time consuming.

As for the KS ... read up on it's function (FSM (98' Max) EC-21 IIRC). I guess I don't notice it much due to being a 5spd and not an auto. Dunno .... I have the code and my MPG's are good, power is good .... can't explain it.

I agree ... clean the EGR (the right way) at the least.

 

I have the same exact codes. Its most likely that the EGR code is causing the KS code. I've had these codes for years, I'm just too lazy to fix them. No harm caused, just a little less MPG thats all.

 

change the knock sensor its worth it unless u want to mess up ur motor. my motor use to knock under full throttle gas mileage was horrible and the motor ran like crap

 

yeah i concur with everyone about cleaning the egr first then dealing with the ks. Because im sure with a clogged egr it would throw off your a\f. and about the ks i would try the resistor mod after cleaning the egr and go from there

 

My car had the CLE come up for Knock as well. You all keep saying clean the egr....where is it exactly and how do i clean it? Just starting in the automotive DIY stuff so still learning. Any help is appreciated. Also someone said its a "ghost" code. what is meant by that? Thanks!

 

I had an egr issue and was unfamiliar with the egr's location too. I then searched and read multiple threads where people suggested that cleaning the egr valve and metal exhaust line running to the valve. I also came up with EGR fsm pictures and cleaned it. The egr valve is located below the throttle body but really look at those pictures instead.

A ghost code is a code that your ecu (computer) register and stores in the memory bank but does not trigger the Check Engine Light.

In my situation the egr was really bad. Replacing it restored lost power (verified my means of my firend's Tundra).

 

Thanks! Looks like I have a task for after work!

 

Yes, change the knock sensor. I got one from ebay, changed it in about an hour (could do way more quickly next time), and the engine works great.

(Post #12 to allow me to start a thread)

 

i got a CEL like 2 years ago took my max to autozone........they said it was the knock sensor, but the day i went to buy the knock sensor the light went off, so i didn't pay it any mind. It came on like a couple of months later after that but stayed off for 2 years. Today it came back off, i dont think that its my EGR valve because i cleaned it when i put my MEVI on, i have a 5 speed so do u guys think its worth changing?

 

Ive got my original ks in my car, of course it went out a 140k. still runs great though.

 

I had the original one at 250k, but it was bad. Replaced it with ebay one and no problems so far.
About the EGR I would say the same thing clean it up, reset the ECU and see if the KS code comes up again