Knock Sensor?

benchmade_boy

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Hello all,

I was wondering if any of you could help me find a knock sensor on my 03 chevy silverado, 5.3 liter Ls edition.

A bad emmisions light came on my dash about a month ago, prior to that it would somtimes come on for a brief time then shut off. But a month ago it came on for good. I just ignored it but finally hooked it up to the computer and it said i had a bad knock sensor. A fellow Ag mechanic told me he had to replace his too, he told me there was one on both sides of the engine block, but for the life of me i can not find it. I looked it up on the enternet and it said it was just above the oil pan, or right by the bell housing.

Can you tell me what this sensor does? I was told it will fail and just tell your computer it is getting bad emissions, but what is the piont of calling it a knock sensor? If it goes out will your MPG get worse? I have noticed my MPG falling but didnt know if this was the cause.

Thanks for any and all help.
 

Superdave

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there are 2 on the LS engines, they are under the upper plenum. the rear one is the most likely to go out as water tends to pool back there.

the knock sensor listens for detonation (too much spark advance) or mechanical knocks and is used by the ECM to control spark advance.

my '00 Silverado had the rear one go out (5.3 Vortec). Eventually the code will go away but the problem is still there.


*edit, this should help out a little.. http://www.jimfancher.com/sierra/p0332.htm
 
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benchmade_boy

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I hope its not under the intake manifold, i really dont feel like taring that apart. I think i read that the MAP sensor was under that not the knock sensor.
 
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benchmade_boy

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SO after reading what superdave posted, yea I will have to take the intake manifold off. I dont suppose there is any differnce from the 00-02 5.3 and my 03 5.3, I dont suppose they changed anything. but you never know.

Does anyone know how complicated this is to change? should I change both sensors since I have it torn down that far?

So dave are you saying there are two on either side of the motor? making four total?
 

Superdave

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nope, there should only be the 2 in the lifter galley. I don't remember there being 4. GM used only 1 for many years..

they are pricey but yah, i'd replace both. The good news is that most of the new GM gaskets are Oring style so you may be able to get away with re-using them.

Before you dive into it, i'd join http://www.fullsizechevy.com/forums/ and see if you can dig up some more info. :thumbsup:
 

benchmade_boy

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Ok thanks for the info guys, I will try and work on it this weekend.

In the meen time woud any of you happen to know how to time a honda trail 90? any info on this would be great.
 
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