Auto Repair Q&A

Popular

Engine

Cooling System

Brakes

Suspension

Transmission

Exhaust/Emissions

Electrical

Body

Interior

Understand

Directory

Auto Repair Products

What is the easiest way to replace the knock sensors in a Chevy Tahoe 2002 V8


Pull the intake and watch out

Pull the intake and watch out for rusted sensors. Water gets trapped in the holes and they can be a pain to get out without the right tools. They also have problems with the wiring harness that attaches to the sensors. You might want to consider replacing it as well. Last but not least, don't go cheap on the gasket set. Get a good one. Good Luck

I'm not accusing you of this,

I'm not accusing you of this, but many folks throw parts at a problem till it's fixed. In the long run that practice turns out to be a waste of time and money. Before you replace the knock sensor,

Tell us exactly what the problem is?

How was it determined that the knock sensor needs replacing?

What error codes are set?

when gas gets below 1/4 tank

when gas gets below 1/4 tank it starts to bog down when giving gas will lose all power and at times will just die. Error code with scan tool comes as knock sensor cant remember the code itself but can check again as the check engine light is on and will come back on after clearing out. every time its the knock sensor

as the check engine light is

as the check engine light is on.

So that we can provide you with the most accurate repair information, we need to know the code or codes that are set. A scan for error codes is free at Auto Zone. Go to an Auto Zone store, have a scan done, and write down the code or codes so you don't forget them, then post them here so we can see them.

Ill get the codes and post

Ill get the codes and post them when I have access to the Tahoe.

Are you hearing spark knock?

Are you hearing spark knock? The knock codes, depending on what they are, could be because the engine is actually suffering from a condition causing the spark knock. Other engine noises can also activate the knock sensors. If the PCM feels that there is actually a spark knock condition it will try to retard the timing. This will cause poor performance. If the PCM isn't getting signal from the sensors (which is usually the case) it can make changes to the timing as well.

i've done a doz. knock

i've done a doz. knock sensors on these, and all have failed because of corrosion.
the well they are fills up with water and takes out the sensor and it' connector.
be ready to replace the sub harness for the sensors also.
if it were ignition detonation, the code that would set would be for timming "est" code, or at least that what i've seen.

As stated before the knock

As stated before the knock sensors are bad about rusting out. Based on the response from mws and several colleagues in the past I want to restate what I said about having the right tools. All too often they are so corroded that the socket that is supposed to fit them will not. In some instances they will even break during removal. If this happens you're gonna have to break out the drill and the extractor set. You will need to be careful to make sure that you don't damage the the female threads on the engine. A good extractor set, if needed will come with centering guides for the drill bit. I'm warning you of this because you would be at the point of no return (as far as the tow truck is concerned) if you can't finish up yourself. One last thing. I've heard of some techs removing the sorry foam insulation that is supposed to keep the water out. In reality it appears to trap the water in and keep the natural evaporation process from occuring. I myself, have not performed this, as the modification is not currently accepted but I know techs that have and swear by it. Can't recommend it but thought you should atleast know about it

i use gms to seal the rubber

i use gms to seal the rubber plugs on the harness, and i have heard storys about them braking off in the block.

when gas gets below 1/4 tank

when gas gets below 1/4 tank it starts to bog down when giving gas will lose all power and at times will just die.

The first thing is you shouldn't be lettin the level in the fuel tank go below a 1/4. You're killin the fuel pump. The fuel in the tank cools the pump, and helps prevent the pump from overheating, so you gotta keep the pump submerged in fuel. Never let the level go below half.

Also at below a 1/4 of a tank the pump is drawing up all the water and dirt that's laying at the bottom of the tank. Just so you know, water is heavier than fuel, and will settle at the bottom of the tank. Since you're lettin the level go down to less than a 1/4 the fuel pump is drawin up that and dirt water.

Well, now that water is gettin introduced into the trucks fuel system. Water bein burned with fuel is gonna cause all kinds of drive-ability and performance problems. It's gonna set codes, and those codes are gonna be false codes. As for the dirt, well thats clogging the lines, and slowin down the oumps efficency. Its's also cloggin the filter and sock screen. Look at it this way. Fuel and fuel pressure are to your truck what blood is to your body.

Doesn't sound like a knock sensor to me. More like a problem with fuel pressure. Replace the fuel filter, and check to see that the sock inlet screen at the fuel pump is not collapsed or clogged.

I'd have to agree with Big

I'd have to agree with Big Block. The knock sensors are not the most likely cause for one to die on you and fuel pressure is. I would of course look into that but when you're done and the truck seems to run great I would still follow up with testing the knock sensor codes. I live in a non emmisions state and some of the jack legs down here will tell their customers "oh that engine light is just for emmisions" they justify this with the owners manual that clearly states that it is an emissions problem. What the fail to realize is that back in the 70's when emmisions first came out they built an engine and threw some emmisions components on it. Now days they build an emmisions system that just happens to also accommodate an engine. All that stuff is there for a reason an can have serious adverse effects on not only performance but also longevity.

ccortiz. 4.8 or 5.3 are the

ccortiz.

4.8 or 5.3 are the same. Don’t wanna know nothing, hear nothing, or see nothing, unless your fuel psi stats are different from below.

Static (KOEO) 55.3–62 (PSI)

At idle and normal operating temperature 45-59 (PSI)

With return line briefly restricted (62 PSI)

Big Block is right. Don't

Big Block is right. Don't worry ccortiz. His bed side manner is always like this. He means well but if you're reading his other posts he's got other things on his brain. Maybe even other brains on his thing. LOL Enjoy the boat ride Big Block.

Maybe even other brains on

Maybe even other brains on his thing.

Good one man, gotta remember that one. :-)

here is the technique,

The link that bfree sent you

The link that bfree sent you to is excellent. Especially for those who don't have an automotive repair data base at their disposal. It should be very helpful if you choose to do this yourself. One thing it doesn't show (and no data base likely will) is all the debris that is going to be waiting for you when you pull the intake. There is a piece of foam on the intake that is supposed to keep this debris out. It probably looked good on paper but real world and paper are two different things. Some are worse than others. You should make sure that as little as possible gets down into the heads. When you pull the intake you will be exposing the valves. Some, of course will be open and that debris can go right down into the cylinders. Use a small vacuum to remove any debris you can. Again, some are worse than others. The last one I did was a farmers truck. It looked like le brea tar pits with a little more crap thrown in apparently for good measure. LOL. It's not that hard to do but you should pay attention to detail. Clean all gasket surfaces thoroughly. Good luck.

I stated it before but I

I stated it before but I did't restate it and drive it home on my last post. You should consider replacing the harness that goes to the sensors. It is easy to do and is often a problem (sometimes the only problem). And again, don't go cheap on the gasket set. When you by a good one and see the difference between it and the original equipment on the truck (assuming it is original) you will think you've really done something and will be proud of yourself for spending the extra cash.

sure seems to be a lot of

sure seems to be a lot of wasted breath here lately, most be just for points, there was a time here when people just wanted to help some one.

mws, You might not be

mws,

You might not be addressing me but the placement of your post is suspicious. It does bring up a question I've been wanting to ask but haven't because it could be considered to be insulting. All across the web and the newspaper ads everyone is given something out for free. It is seldom the case where this becomes a reality. That's why I don't pay them much attention. I can't say I didn't notice this "free gas card" but I can say it has nothing to do with what I post here because I, once again have not bought in to the whole "free" thing. Do people actually receive these cards? Is there not some other impossible hoop to jump through once you have "won"? You commented on "wasted breath". Very tactful. If you don't like the input from others or myself, that is an opinion of yours I would be glad to accept as I'm not here to prove anything else to others. If you knew me you would know that I spend alot of my time helping others expecting nothing but maybe a thanks in return. The input I give might be cosidered useless to you but it is genuine on my part. You might want to consider that before you add insulting comments like your last one. It is a reflection on your character and could be misconstrued as "sour grapes". I'm sure that's not the case though. You're just here to help right? Congrats on your gas card.

Ccortiz, This posting is

Ccortiz,

This posting is turning into a three ring circus. I’m just gonna take a moment here to put things back into their proper perspective. The problem you are describing is a drive-ability and performance issue. As with all drive-ability and performance issues the basics have to be checked first, before you go lookin for a bigger problem. Just to make this easy, I’m gonna list the basics below that are standard to any drive-ability and performance problem for any vehicle with an internal combustion engine.

Problems related to fuel pressure and fuel volume
Problems related to engine vacuum leaks
Problems related to cylinder and ignition misfires
Problems related to ambient air introduction
Problems related to exhaust leaks
Problems related to excessive exhaust back-pressure
Problems with cylinder compression

Don’t misunderstand. I’m not sayin that you don’t have a knock sensor problem. As a matter of fact, the setting of PO332 is common for your particular vehicle, but even if PO332 is set, it doesn't necessarily mean that the knock sensor needs to be changed. I’m gonna end it now, because my goal is to keep this simple, without getting technical. Trust me guy, I can keep goin with this and just blow your mind, but I would never do that, because it wouldn't be fair to you, and that's not what this forum is all about. It’s only been a couple days, and I know it’s the summertime. The first chance you get post the results of the fuel pressure test mentioned above, and any error codes that may be set. If you can post the results of all the above mentioned basics. If you can’t, then that's ok, but at least let us see the fuel PSI stats and any error codes. Thanks man.

J

BTW, If PO332 is set, (and all the above basics check out) apply TSB #02-06-04-023A

if it only bogs down at 1/4

if it only bogs down at 1/4 tank. checkthe fuel pressure before 1/4 tank and then again at 1/4 tank---it should be the same. if there is a significant drop in pressure, suspect problems with the fuel pump inlet hose(s) in the tank. however, before removeing the tank be sure to check the pressure at the line before the fule filter (when tank is at 1/4) to see if it's low there as well.

Let us know how it turne out.

Let us know how it turne out.

Ccortiz, Where are you in

Ccortiz,

Where are you in terms of resolving this? Haven't seen a response from you lately. Do you still need our help?

once you replaced the knock

once you replaced the knock sensor, did the code come back?


Auto Repair Q&A Contest

Win Cash!

Participate in the 10w40.com Q&A community to win cash prizes!

win cash prizes

Congratulations to our September Winners!

How To Play

 

Top Contributors: 3 weeks