Does bypassing a knock sensor risk damaging a GM Vortec V8 engine

[@countrybussin]

The thing is, most people that do this are on a budget to begin with. Add to that the fact that they have an old truck, with an old engine. People are going to Monday Morning Quarterback you no matter what. At the end of the day your 2002-2006 Chevy or GMC is still getting you to work everyday, and that's the goal. All engines will break eventually. Thanks for the info!

[@jamesbrasch2617]

I agree with what you are saying but as of people like me that are going with a big cam and a tune a nock sensor malfunction can cause major damage for a factory engine if it was me depending on money would be the factor of replacing the sensor or deleting it completely now with my engine it’s getting a big cam aftermarket throttle body headers and a high volume high pressure oil pump with .660 valve spring and a set tune I am deleting the nock sensors and the egr simply to make my combination more reliable great video and I feel you are 100% correct

[@alfonzobrown1703]

Thank you sir. I had just gotten my 2005 Avalanche out of shop from a $900 bill for torque convertor, flexplate, seals etc. Next day my truck threw the knock sensor code. I did your fix right away. I believe the fuel had went bad from it sitting until I got the cash to do the transmission work. Needless to say, it works. I had no desire to put it back in the shop. So I thank you.

[@andylarson3547]

I bypassed mine on an 2005 236k truck Worked great. Good short term solution. If you have an old dog, just bypass it. Probably won't hurt a thing. If you have a knock, you're in trouble anyway.

[@SoaringMech]

Good news. I had a long talk with a friend who is a Mercedes trained automotive tech about knock sensors. 1. The ecm does NOT use the knock sensor for anything except when it detects a preignition. 2. If you have a well maintained engine and use the correct octane fuel, it will not knock. 3. If motor has two knock sensors, the second one is just for redundancy. If one dies or is bypassed, the working one will detect all the knocks and the ecm will retard timing to prevent the knocking. So the bottom line is that bypassing a failed knock sensor does not risk damaging your engine.

[@SoaringMech]

@Brett Collins According to the Mercedes trained mechanic, the functioning knock sensor will hear the knock and the ecm will still retard the timing to protect the engine.

[@dustinbailey3766]

I did it today and feel confident now i got a knock sensor kit i dont need lmao

[@mister4053]

Hey I just replaced both knock sensors and harness and cleared codes. Now they came back. Should I bypass my bank 2 that is throwing a code again or do a external knock sensor on side of head? Or do the ECM reset with engine revs to accept my knock sensors?

[@plummerspc]

@@mister4053 Caleb, I did mine bypass yesterday. Figured it was worth a try.. Incredible the gain of power that was missing because if a retarded ignition. The passing gear was almost non- existent. Now it is running like a beast. I double check plugs to make sure they had not fouled. I had only driven maybe 30 miles total once code first appeared. the ecm should be able to differnceiate the difference between bad ground situation and a true knocking. Until that happens. the whole concept is lame.

[@mister4053]

@@plummerspc bypass by doing the Rev thing? Or by wiring it to only use the 1 knock sensor that isn't throwing a code? I replaced the sensors and harness with "Dorman" Kit but the code came back bank 2 isn't reading right again. I also put in new double platinum plugs and wires the other day as well

[@teagreen2220]

In olden times the knock sensor was our ears if you were a tuner of engines. The extra stuff added to today’s engines makes them more complicated in an effort to discourage diy auto repairs. The high octane timing tables are so low in timing that removing the knock sensors will probably not ever harm these engines. Best of luck to all. Thanks for these informative videos!

[@davidkeddy7717]

Your 100 per cent right , you can tell when an engine is pinging / knocking. you can hear it when you accelerate, And @ those times you dont even need a sensor to to tell you that ! God gave us all "EARS " to hear it ! And the guy is right, it's masking over a problem, wereas if we just relied on our own ears, we realize we have a problem and would begin to get to the root of it and begin to fix it

[@stasstasov5176]

It’s great to hear that I’m not the only person who did this. Now I’m worrying less that it can kill my engine. However, I really tried to fix the problem by replacing the both sensors and the wires kit...unfortunately, it was all in vain. The problem code P0332 did not disappear for some reason. Perhaps it’s because I had bought non-original wires DORMAN..So, I guessed this gimmick could help, and it really worked. Now I’m pleased to hear I’m not going to put the engine down. Thank you Sir!

[@SoaringMech]

That’s strange. Not sure what could cause the 332 after you replaced both sensors. But you should be good to go with the bypass.

[@stasstasov5176]

sam washburn I suspect that the guy, who I entrusted to fix this problem to, didn’t clean the sensor’s seat well enough.

[@SoaringMech]

Stas Stasov . Good point. That would explain the 0332 code after replacing the sensor

[@rodneykahn6927]

@@stasstasov5176 vs DOA part right out of the box

[@sheepishmclemmingston5550]

Could have been the electrical leads(wires) themselves, corrosion due to moisture infiltration can do it. Could have also been the plug pin where it connected to the ecm or pcm (whichever your rig is equipped with) could also be a faulty ecm or pcm itself, where that read out connection itself faulted, burned boards and other damage and breaking of a circuit can happen in many fashions internally on a circuit board from many reasons. What this gentleman has stated here though is absolutely correct and you risk very little to virtually nothing by doing this bypass.

[@speakbigtruth9383]

I love how much you learned about this. Very impressive.

[@MelvinCalvert]

In the New Webster’s Dictionary, under the word “genius,” the first definition is “Sam Webster.” If it’s not, it should be. Sam, I hope you are a Teacher. If not, the works has missed a chance to learn from a master. Amazingly great instructional videos - starting with how to bypass a faulty knock sensor on GM V-8s. Thank you.

[@SoaringMech]

Thanks Melvin. Glad it was helpful.

[@MelvinCalvert]

Sam: My 2009 Yukon set the code for low voltage on the Bank 2 sensor. After watching both of your videos, and having recently decided to keep and drive my (71,000 miles) Yuke and replace all the brake (wheel) components, I have arranged to have my local GM shop replace the harness and both sensors. I have always maintained the vehicle and it has NEVER knovked, but I have noticed since the CEL came on, that acceleration, especially going uphill, has lagged oddly. The tab is about $135 for the (NAPA) parts and 2.5 hours at $85 an hour. Cheap fix to keep things working. Again, these two videos are so stunningly effective in communicating a pretty obtuse problem/impact/solution, that I watched both twice. You do have a teaching gift!

[@MelvinCalvert]

@@SoaringMech Sam: After having my GM shop replace both knock sensors on my 2009 GMC Yukon, they deleted the code, and said all was well. Two blocks away, the code came back. After driving directly back, the tech spent three hours checking the harness between each sensor and the ECM and then replaced the Bank 2 sensor (again), and deleted the code, removed the battery negative cable, waited 45 minutes, reconnected the battery cable, and restarted the engine. Again, I got the “It’s fixed,” line. Got in, drove about a mike and the CEL returned. Back to the shop. After another hour, I was told, “It has to be in the ECM. “ I left and still have the CEL and I do think the engine is acting sluggish when accelerating. May I please bother you for your thoughts on what I need to do to actually get the problem causing the CEL resolved ?

[@SoaringMech]

@@MelvinCalvert exactly what code(s) are you getting?

[@MelvinCalvert]

@@SoaringMech The same OBDII Code that started the process, P0322, saying the circuit for the Bank 2 knock sensor was showing low voltage. I don’t have my original notes where I am, but I think I put the original code in my first query to you. (Sam: I just edited this message. It was waiting ti be launched, but I thought it launched about four hours ago. )

[@m.c.2349]

I'm a competent mechanic. My same year Crown Victoria doesn't even have knock sensors... So I didn't mind using this shortcut. If I were to dump a bunch bad gas in then maybe the knock sensor would help. BTW, ask any tuner how useful LS knock sensors are... Not very

[@vinceporter228]

Great vid. Looked at your first vid on this issue. This is an excellent followup and answered the questions that arose from the first vid.

[@richc9503]

Great explanation, I was asking myself the same questions when I looked at the way the system is set up and initially came to the saame conclusion but I wasn't questioning it as much as you. I was going to replace everything. After watching both of your videos I'm going to run with your decision and bypass the 2nd sensor as you did. I've never heard my engine ping since I've had it, actually with the newer systems and fuel we have today I haven't heard any enging ping or knock since the early 80's unless there was a real issue mechanically. Thank you!

[@ogfromutube9649]

The ECM reads burst knock retard, as well as knock counts on any cylinder or overall engine depending on software. There are so many factors for ignition timing. You have idle maps, base maps, power enrichment maps, as well as iat and ECT adders based on rpm and temperatures. The stock maps for an LS ignition timing is conservative and unless tuned chances of knock are slim. Unless you got some really poor fuel, burning a lot of oil, or went super lean from bad injector/coil, weak pump, or clogged filter/regulator. If most of those instances happen the knock sensor wouldn't make much difference. The ECM has other ways of entering "limp" mode which would safeguard detonation. Usually an active misfire will cause a flashing light and limited rpm/power. Cars ran for years without knock sensors and with no engine management at that. Now if your running a modified car/truck and looking for peak power. Then knock detection is pretty darn important. Many ppl tune in that manner. Run on a dyno keep adding timing/boost until you detect knock, run out of fuel capabilities, or start losing tq vs gaining it. In that scenario it could be quite dangerous. Especially without a wideband oxygen sensor to keep fueling target in fast response and accuracy.

[@jonwexler8194]

Watched your video. Bypassed sensor . Works great. Thanks

[@davidkeddy7717]

I'm watching and listening to every one's posts and the man's video, and I'm sitting here thinking about it all. If an engine is really not knocking, and it's just the ECM that's not happy with the sensor, because it's a bad sensor, why couldn't one just buy a new sensor , fabricate some kind of a bracket to bolt onto the head or block, or even any where just to pick up a ground somewhere, just to satisfy the ECM and rid the code. And again, if you know your engine , and it is well maintained. And everybody can here an engine pinking/ knocking with your own ears. Since it' only a single wire lead, and just looking for a ground for the base of the sensor to ground , it should work just as well. Someone tell me why this wouldn't work also. Beats tearing the whole engine apart just to satisfy the ECM on an engine that's really not knocking. Thanks Dave It's just mounting them externally instead of internally, should receive the same results, and just leave the two bad ones inside the engine alone.

[@SoaringMech]

@@davidkeddy7717 you are correct. Some people do that.

[@davidkeddy7717]

@@SoaringMech Hey! Thanks for your comment, And thanks for agreeing.

[@chrismunos7741]

Thanx Sam. I'm running an LS2 in my '79 Camaro with a 24x system. I have the typical knock non compatibility issue between the 24 and 58x systems so I'll be deleting the knock sensors altogether. It appears that a 100k ohm resistor ran on the sensor wire to ground will do the trick. Engine is freshly rebuilt and runs strong. I share your belief that the sensors only do anything when there is an issue from improper fuel, etc. This will be temporary, as when I pull the engine again I'll drill and tap the sides of the block and add the single wire 24x sensors.

[@SoaringMech]

I like your approach. Sounds like a hot car. You may need to use a 100 ohm thermistor rather than a resistor because the ECM expects to see the knock sensors resistance vary as the engine temp increases. Let me know how it goes.

[@Beardforce1]

What happened was this. You posted a video about knock sensors. I happen to have brand new knockers. You allowed me to check those...still new, and realized the purge hardline fitting on top of the intake was broken and leaking horribly. Either way. THANK YOU! Brand new motor never ran so good!

[@b_aleman]

Hey Sam, Thank you for taking the time to make these two videos. Lots of good info. My scanner was telling me that my 5.3 was running rich on Bank 1 and bank 2. The dealership is telling me the cause are bad knock sensors. Does that sound right? Could bad knock sensor cause rich codes with no knock codes?

[@SoaringMech]

If the ecm thinks both knock sensors have failed, I’m guessing it may enrich the mixture as a precaution against knocking. But I’m skeptical because it would be unusual for both knock sensors to fail. If both have failed you should have a check engine light and codes p0332 and p0327. How old is the engine? Do you drive through lots of puddles. Water at the top of the engine causes the knock sensors to rust and fail after 10-15 years.

[@dziggy3004]

Hey Sam! @ 7:15, you effectively suggest a knock sensor only has a binary input (from detection), that the analog degree of the strength of the knock (a pounding vs. light taps) does not vary the produced output -- but a simple test harness of tapping on the engine will prove otherwise. A single BIG tap will yield more AC voltage output than single small taps -- it's not all in the frequency.

[@SoaringMech]

Thanks. That’s useful information. I’m guessing that the ECU reacts the same way regardless of the knock intensity, but I could be wrong.

[@dnickens20115]

Hello Sam, i have a 05 v8 6.0 Silverado which had a bad knock sensor check engine light. I did your mod and have been driving for approximately 300 miles now check engine light went out by itself and I just wanted to say thank you.. save me some money did not want to go through the process of taking the intake off and replacing all that mess.. I ordered two sensors and the wiring harness off of Amazon so now I have a spare sensor just in case one goes out.

[@1voorhies]

Thank you for posting this. I just bypassed one of my knock sensors on my 2001 Silverado after getting a P332 code. I used your first video for guidance, but was worried about possible long-term negative effects from only having a single remaining knock sensor. This this video assuaged my concerns about that. Do you know how the ECM responds when it senses a bad knock sensor, i.e. does it think that the engine is pinging and retards the timing or does it just think that the sensor is bad and doesn't do anything to the timing setting?

[@SoaringMech]

I dont know. On my truck, it ran fine with a p332 code. Others have posted the while having the p332 the truck ran badly, but after bypassing the bad sensor, it ran much better. I do know that my truck has run perfectly for three years since I bypassed. But I’m religious about keeping the engine well tuned and clean so it never pings. So in my case the knock sensors have nothing to do.

[@outfield1988]

I appreciate your videos. Replaced both my knock sensors on 6.0 l Yukon. Job was some work but not too bad. Hardest thing was injector connectors. Code come up after 20 miles’ I did drop one so could have damaged it. Cleared it so I will see if light comes back on.

[@SoaringMech]

That’s a drag after all your work. Did u get cheap Chinese replacement sensors? Those are known to be a scam. They don’t even detect knocks but make the ecu think they are legit so the trouble codes go away. Good luck

[@jeremywilson1299]

50 % of all knock sensors are known to be bad from factory, even the “quality gm replacements” are made in Serbia)

[@vwright9716]

I just replaced mine in my truck, put goo around them so they wouldn't get wet. It was a few hours but not really a huge challenge financially or mechanically. That being said, if something odd occurs and I have to do it again, I will try this method. If you are going to do it the correct way, use ac/delco sensors or you will do it again.

[@Wildkat-1]

I don't know if the difference in resistance from 1 sensor to 2 would cause failure or code tripped over time or not...the no cost part is attractive though... !

[@maxmusterman6030]

Thanks a lot dude! I own a Jaguar S type, it's a hell to change the Knock sensor, but I did it just to see it was the wrong sensor I ordered 🙄 I now ordered a genuine one, but Im thinking of just plug in a resistor and do the proper KS change sometimes later 🤔 I guess I will use premium fuel for this time just to be sure.

[@scottfenton7607]

Thank you for your video I'm thinking of trying to bypass my! We tried to contact 2 new knock sensors and harness and it's still throwing P0327 I think. But I'm going to try a few things!

[@crautoguy8384]

well you have one option or 2 shouldn't really matter it's in the engine valley. Older GM engines the original style small block 5.7 and tbi 5.7 have the Knock sensor are on the side of the block Is passenger side i believe it's been a while. Even before obd2 it's just code 52 I think i can't remember that far back. Most of the time that code was for a wiring problem l the sensor I believe that you are correct sir that 1 in the engine Valley should be able to hear Knox and paings. Then adjust the timing appropriate. Remember there are 8 cylinders so if you have a reduced octane fuel under a high engine load that 1 sensor is going to pick it up for the 4 cylinders it is supposed to sense it for. LS is kind of a oddball design because those sensors are in line front and rear they call them bank 1 bank 2 but they Don't sit on each side of the engine as is bank 1 bank 2. Is so theory as to reason. I've been doing this for a long time that if you have one function you're nonsense or it can hear the knock from the back half or the front half of the block that is designed to hear the rest of the cylinders will be under the same Conditions and load. My highly educated 26 years as a professional technician owning my own shop and used to have a California smart license but lead me to believe that this Is work around for work just fine. I have had issues on trucks where I had the intake manifold off to fix the lower Is valley seal that was leaking. Replace the nonsense just to do do diligent. As I know these are an issue the front one was full of water surprise. So I cleaned it up replaced it and now I have A Knock center code from the front Sensor that comes and goes. Is that Whole whether nonsense or recesses into the block was extremely rusty when I did the original repair now I'm having issues this is the perfect fix for these issues.

[@jacobstinchcomb1922]

Helped me, awesome helpful video. Thank you Good sir!

[@lennysexoticfamily57]

So what exactly do you think would happen if you buypass both of the knock sensors

[@SoaringMech]

If you bypass both, the ECU will not know if the engines knocks. If it does start knocking because you use cheap gas or something like that, engine damage would occur. However if you keep your engine tuned and clean and use good quality gas of the correct octane level, it should never knock, so it wouldnt be a problem bypass both sensors. However, if you bypass both (ie disconnect the wire harness, the ECU will think that both knock sensors are defective and will throw two codes. P00032 and P0029. It may also adjust the spark timing as a precaution which would lover your power and gas mileage. Hope this is helpful.

[@J.Crooner]

Cool advice & great informative video. By the way before you bypassed the sensors did your truck have a loud whirring noise & loss of power? On my hummer h2 this seems to be the issue & also when I hit the brake while the truck is parked the noise gets louder. Now it appears to be some oil leaking from front bumper on passenger side which I'm more concerned about now if that's what it is. I'm hoping it's just a busted hose or something simple. Not sure what it all means but hopefully I can make the fix. Any insight would be gladly appreciated thanks👍😁💪😎💪

[@SoaringMech]

I’m pretty sure I know your problem. On the gm pickup trucks the hydrolic pump for the power steering also provides hydrolic pressure for the power brakes. That pump has a fluid cooler mounted in front of the radiator. That cooler can rust out and leak fluid. When that happens the pump screeches for awhile until it runs out of fluid and stops doing its job. If your hummer is similar, that’s your problem. This happened on my Silverado. So check the fluid level in your power steering pump. If it is low, then check for the leaking cooler in front of the radiator. On the Silverado it is on the driver side. Replacing the cooler is pretty easy and they are not expensive. Don’t drive the truck for long with low fluid or the pump will need to be replaced. Good luck. Let me know how you make out.

[@J.Crooner]

Thanks a lot I really appreciate this info & I'm going to do exactly what you said. Since I see the fluid has leaked out would you say I should replace the cooler or can I simply refill the power steering fluid to proper level to take care of the problem. I can imagine I probably will end up doing both but only if it's necessary👌

[@SoaringMech]

JASON SQUIRE I just posted a new video on how to replace the power steering cooler. It may be helpful for you.

[@SoaringMech]

kzbin.info/www/bejne/iGGXd6N7aqZ6jqs

[@SoaringMech]

JASON SQUIRE do u figure out what the problem was?

[@theamerican7080]

Thanks Sam. Appreciate the comprehensive explanation.

[@wesleysandifer6157]

In a nut shell. If your engine is running like it should, your knock sensor will have nothing to do. If your engine is pinging then you got some other issues to look at. Makes sense to me . A wore out timing chain could cause pinging. Something to look into anyways.

[@warrenlancaster8045]

Knock sensors detect knocks not audible to the human ear and pull timing. Once the knock is audible, 9/10 damage has already been done.

[@bakntheday]

Great explanation.

[@flyingscot3666]

Thx Sam - great video - well considered position - however I kind of disagree based on recent practical experience - 04 Yukon 6.0L - car was running terrible - got the knock sensor code - P0332 - changed both knock sensors and harness - car now runs super smooth again (just like new) - plugs and leads are new & I use 87 gas - maybe if I used higher octane gas car would run better with defective knock sensors - didn't try that (wish I had) but overall I am glad I have done the job (myself) - piece of mind. If I had continued the engine would undoubtedly have suffered a failure due to the high level of vibration (knock) that was present. I would not like to trust to high fuel grade to avoid knock, especially on an engine with 200k miles on it - trying to keep it going.

[@SoaringMech]

Interesting. My 6.0 vortex has continued to run perfectly three years later with both inputs wired to the working knock sensor. It could well be that the good sensor is detecting any knocks that do occur.

[@flyingscot3666]

@@SoaringMech u bet - If I had seen ur bypass technique I would have given it a try but now I've done the job I'm happy enough - it is doable - it seems to have been successful - there is a great video on KZbin - but the job is definitely involved and not for the feint hearted 👍

[@flyingscot3666]

@@SoaringMech what gas you run the 6.0 vortex on? its same engine as mine so good for comparison. I think you may have a point re the one sensor doing the work of two - could be exactly what's happening.

[@SoaringMech]

@@flyingscot3666 87 octane works fine

[@flyingscot3666]

@@SoaringMech when I took out the old sensors from my engine they both gave the same sub-normal resistivity - 50kohms - (new unites were 100 ohms) - therefore suspect that both of my sensors had failed - the fact that your engine currently works fine on 87 and mine did not prior to both knock sensors being replaced indicates that one of your knock sensors is still functioning. But of course this is just schoolboy logic & there may be other issues. Anyway - thx for the info Sam - hope your truck runs long and trouble free.

[@christianortiz2834]

Did it pass smog?

[@SoaringMech]

Yes. Absolutley

[@jrobertson7527]

I had a lifter thaf was sticking when my 02 avalanche hydroseized on me i replaced the intake gaskets thats when I discovered the knock sensors mine were rusted and corroded so I left them as is i went on and put all parts back on without replacing the knock sensor thats been over a yr. Now and setting at 348,000 and my daily driver id say the knock sensor does not effect the way the motors runs.

[@335135]

My question is I’m doing a ls swap and keeping the fuel injection system can I just remove the knock sensors and put a new valley cover without the holes or is there more that needs to be done

[@SoaringMech]

You can probably do that, but the ECM is going to want to be connected to a knock sensor(s) somewhere. Some people have successfully mounted a knock sensor(s) to the outside of the engine (bracket on the front). That way the ECM doesn’t throw codes. But be aware that the knock sensor will not hear any knocks. So you need to keep the engine very wells tuned and clean so it does not knock at all. That’s what I have done.

[@stevefowler9822]

Just as a fyi, had a both knock sensors on 05 gmc5.4 replaced, full tuneup ran fine till I put my foot in it getting on freeway, knock sensor showed up again, figured out I got a bad tank of gas from my favorite big box store, put a bottle of octane boost in and haven't had any more problems. I'll put in a tank of premium next fill up, hopefully no more problems

[@SoaringMech]

If that engine is designed for regular gas, you should NOT need to put hi octane fuel in it to prevent knocking unless you are pulling heavy loads. Something else is wrong. Are you running the correct good quality spark plugs that are not worn out? Has carbon built up in the cylinder heads causing over compression? Are you running too lean for some reason (faulty mass airflow sensor?). My truck never knocks on 87 octane, but I do put 89 in it if I’m towing a big load. To clean the cylinder heads, run a couple of cans for gum out fuel treatment through it. Hopes this is helpful.

[@stevefowler9822]

All work done at local gmc dealer, new plugs, wires, fuel injector flush the works,truck put on scope sensors working as programmed

[@SoaringMech]

Steve Fowler is it still knocking on regular gas from a name brand like Mobil?

[@joshrozeboom5316]

Hello! Could use your help on this ordeal. Replaced both with the gasket and wire harness. Did a continuity test between PCM and wire harness connection and that was good. Did an ohms test on the sensors via the harness connection and got around 100k on both. Only throws code for the front now after replacement. Is this a PCM issue that even if bipassed it will still throw the code because the problem has nothing to do with the sensor?

[@SoaringMech]

Disconnect the sensor wire harness. Then use alligator clips to cross connect the wires coming from the PCM to the opposite knock sensors. Then run the engine and see if it throws the same code or the code for the other sensor. If its the same code, then the PCM or the wire to the PCM is faulty. If its the other code, then the problem is the sensor. Im guessing that one of your new sensors is bad. The ohm reading you got is in the correct range, but the PCM expects the resistance to change as the engine heats up, If it doesn’t change by the right amount, it throws a code for that sensor. Good luck. Let me know how it turns out. The good news is that you can use my method of connecting both wires from the PCM to the good knock sensor to get rid of the code. Your engine will run fine that way. ITs been almost 3 years for my truck and its never had a a problem.

[@scp8439]

Thank you. I have a 02 Tahoe with 324K on it. It just now throws a knock sensor (bank 1).

[@CHawkens]

Check your knock sensor circuit plug, check each one if one of those wires detects a lower ohm rate that the other one. just bypass it. 02 to 07 LS / LQ9 5.7s - 6.0s GMC trucks will be fine doing so, as long as you know your engine is running good, oil changes and maintenance is always kept up on the motor. then, you can bypass the faulty knock sensor. Due your research and check all variables at your own risk.

[@robertthurston6858]

I will try this. Everything you've said sounds reasonable. But I was wondering how a garage can charge $1000 to do the replacement of the knock sensors if videos and comments show backyard mechanics doing this job in 2 to 3 hours ? I'm going to ask my garage mechanic what his time estimate is. Thanks for the insight.

[@digi3218]

It does only take a few hours if you know what you are doing or done it before. I have done it before and it almost went smooth except I slipped and hit the heater core hose and broke the plastic connector. It needed replacing anyways but I waited until the next day as it was getting dark. I guess I used cheap knock sensors because I'm getting a code again (probably half a year later). I would love to go this route but I'm going to get some ACDelco sensors this time and do some things differently like dielectric grease on the threads, etc.

[@digi3218]

I want to do this fix but not sure if my OCD will let me. It honestly seems like it wouldn't be a big deal. Also I use 89 gas so there is less chance of knocking.

[@dbspecials1200]

My thought was, can a new sensor simply be "relocated" to an accessible area of the engine, but still detect detonation and provide the signal to the ECM? maybe on a little bracket somewhere? drill into some solid aluminum somewhere? 🤔

[@SoaringMech]

Yes. Some people do that. It gets rid of the code. But not sure how well it detects knocks. There is a bracket on the front of the engine that it can screw into.

[@gregoneill1495]

I have over 300k on my ‘01 4.8 Sierra, code P0332, going to do this fix!

[@Leo-cu1yq]

Thanks you for knowledge

[@user-cl5ov9dx5o]

If you do not notice engine is knocking...please have your hearing checked.

[@JohnMeyer]

My check engine light went out after splicing the one knock sensor to the other on my 2001 Toyota sienna but it still knocks (pings) under load especially when it's warm . Probably gas seems to help a little but doesn't fix it.

[@SoaringMech]

There’s a lot of reasons for knocking. You need to get that fixed

[@highrisk5510]

This isn't a "fix" video. This is a temporary bandaid IF the sensor is just bad to get you by til you can replace the sensor.

[@jeladsnikpoh1289]

Thank you for the vids. I have a conservatively tuned envoy 5.3 v8, just got the codes for BOTH knock sensors after cleaning engine bay (p0332 and p0327), so I don't believe this bypass method will work for me. I have an onboard diagnostic tool that I just delete the 'pending' codes before they become 'current' codes. The vehicle runs great, absolutely no knock, I'd rather just erase the codes before they become 'current'. Is there any risk of retarded timing or anything if I just do that instead of replacing the stupid things? It's slightly inconvenient, but so is bypassing/replacing them. I just want to confirm with you that the computer isn't pulling timing with bad KS, resetting codes before they become 'current'. Does the computer automatically retard the timing for bad sensors, even though there is no knock? If so, is it only after the 'pending' code becomes 'current' (after a few ignition cycles)? Thanks in advance if you can answer!

[@SoaringMech]

Great question. Heres a link to a video where i explain how the timing is adjusted. kzbin.info/www/bejne/il7WepuIhqeBnbs. However, we have never figured out if the ECU takes pro-active action when it thinks that both knock sensors are bad. I would suggest, connecting a code reader to the engine that can display the timing degrees in realtime while the engine is running and warmed up. You will want to show timing degrees and RPMS simultaneously. Capture that information for several RPM levels including at idle. Then compare those to the correct levels which you should be able to find somewhere on the internet. Good luck. Let me know what you find out. Also. Your knock sensors grounding threads got corroded when you washed the top of the engine. Thats why they failed. Its a known problem with these engines caused by the location of the sensors in the V at the top of the engine where water can collect.

[@SoaringMech]

You’ll have to find a graph like this for your engine. www.gmsquarebody.com/attachments/timing-curve-snip3-png.117669/

[@tennesseehunter3190]

98 GMC 5.7 vortec.....the knock sensor is under the truck close to the starter .....been having a miss for a year....cleaned maf, new plugs, wires, dist. cap, coil, cleaned the egr and truck runs fine UNTIL i try to keep it at a constant speed like 40 mph --65 mph it misses . Constant speeds ( using and not using cruise control doesn't matter ) PAST 70 seems to run fine . Took it to have it scanned says knock sensor lean bank 1.....truck has 230 k miles on it , idles fine runs fine when gas / power applied ..no lifter noise or other knocks/ pings so sounds good . was wondering how to bypass the single knock sensor or just leave it unplugged ? ..got any info on the 98 and older knock sensor problems and cures to delete the thing instead of reinstalling another one ?

[@SoaringMech]

That’s a tough one. “Not sure what knock sensor lean” means or why it refers to bank 1 which implies there is a second knock sensor for bank 2. Try disconnecting the wire that goes to the knock sensor and see if there is any change to the engine performance. If it runs the same, it isn’t a knock sensor problem.

[@tennesseehunter3190]

@@SoaringMech ok thanks

[@51-FS]

Just replace it seinc its easy to get to...

[@shawnchildress2198]

I'm getting a c o d e coming low circuit and low voltage can I just replace those things yet brand new ones Royal pain-in-the-ass LOL you weren't kidding about that..with my own mater I'm getting the same reading of 99.5 out of both sides which what should I do

[@dougshuckra2063]

I can understand why you would bypass a bad knock sensor in this case but my truck has 2 good knock sensors in it. Ohms are both at 100.3k from the wire harness plug pin to ground and both are seeing a small jump in mV when I tap on the block yet I'm still getting the code for circuit low on bank 2. The sensors have even been swapped and still bank 2 is the issue. Resistance back to the ecm thru the connector is the exact same too. If I'm able to get readings from bank 2 that are the same as bank 1 I'm at a loss as to what the real problem is here. Any ideas?

[@SoaringMech]

Sorry for the slow reply. Your situation is puzzling especially since you swapped the sensors. I believe that the ECU expects to see the resistance thru the Knock sensors change as the engine heats up to operating temperature, and will fail the sensor if it doesn’t. Try checking the resistance thru both sensors with the engine warmed up. Do it with engine running and not running. You should get identical readings for both sensors. If not, that may be your problem. Let me know what you find.

[@jrobertson7527]

That is not possible.

[@michaelfite5273]

Can they be tuned out on an 05 tahoe? I like this idea but if I'm getting it tuned and they can be tuned out without causing problems then I want to do that. Any info is helpful! Thanks!!

[@SoaringMech]

I would say yes. A well tuned engine using the correct octane gas should never knock so the knock sensors are not needed in that case. Although if u pull heavy loads on hot days, I would use 93 octane just to be sure.

[@michaelfite5273]

@@SoaringMech I appreciate the quick response brother! Thanks!!!

[@T-REX72]

Maybe it isn't a bad knock sensor, maybe it is a bad engine. ??? any thoughts?

[@SoaringMech]

No. If you get that code the sensor is bad, or the wiring to it is bad, or the way it is grounded is bad because of corrosion. See my other video about how to trick the ecm into thinking it is good.😊

[@T-REX72]

sam washburn ok. Thanks

[@sircampbell1249]

2001 on two wires into one... replace on outside...

[@captaineo8399]

Would the wrong coolant or a faulty coolant sensor on an 05 suburban 5.3 ls give me a p0327 code?

[@SoaringMech]

No. P0327 means faulty knock sensor

[@GabesaNinja]

I replaced mine twice and it's still giving knock 2 CEL. I'm considering this because the engines been retimed and gaskets replaced.

[@SoaringMech]

As I said in the video make sure the engine is well maintain and use the correct octane gas and it will never knock. New spark plugs, correct air/fuel mixture, clean mass airflow sensor, clean air filter

[@Primal_Dad_Truther]

Just did this after fighting with a shop I bought my truck from. They couldn't figure it out and couldn't fix it. I'm going to look like superman to my wife if this light stays off 😭😂

[@warrenlancaster8045]

Find someone with HP tuners or buy it yourself and have them turn the code off. For $100, to unlock the ECU, you can turn off any idiot lights, turn up fuel enrichment, and do whatever you want indefinitely.

[@michaelwright5585]

It will cause a fault on the good knock sensor. Basically, just replace both, with the harness. Use the upgrade felpro kit also.

[@SoaringMech]

Of course replacing both along with the wiring harness is the best solution. However, many people owning these older engines can’t afford it and dont want to risk breaking something else when they pull and replace the entire intake manifold. GM made a poor decision when they placed the knock sensors under the manifold.

[@steve7settle394]

Which knock sensor is number one which is number 2 on a 5-3 2000 model

[@SoaringMech]

Blue wire goes to bank 1 knock sensor, green wire goes to bank 2 sensor. Code p0332 means bank 2 sensor is bad, code po327 means bank 1 sensor is bad

[@haroldthomas1031]

Does a bad knock senor cause a engine to stall ? That's what I'm going through I use a guage from a parts store and it said that my engine had a bad knock senor

[@SoaringMech]

I don’t think a bad knock sensor would cause it to stall. Something else.

[@jeremywilson1299]

It would cause a hesitate under load, trust me. If it is causing the engine to retard one way or the other, in other words the engine adjust the timing to counter what the knock sensor is showing if it is reading incorrectly than yeah it very well could. Cause hesitations not necessarily a stall out but you may think and it may seem like it is going to stall. Any good scan tool should be able to show u the knock retard percentage the comp is adjusting for due to knock sensors. I just went through this with a vehicle with what I thought was just fuel problems. 2004 5.3 engine. True gas non flex. Was showing lean codes, knock sensors codes and misfire codes, had new fuel pump, new plugs, wires, and mafs. When it was brought to me. And It was still running 85% lean both banks. Would act crazy under any load but great under 20% loaded. Did a fuel pressure test, showed good until wide open throttle, n only lost a couple lbs, found two exhaust manifold leaks, fixed them. Lean % came down some, ran some better, but still hesitates under load, ok, than I went ahead changed fuel pump due to the pressure under load dropping a little at wide open throttle. And it was acting up like a regulator would, and since reg, filter and pump were all combined on it, inside the tank. It all had to be changed. Put a factory gm fuel pump in it. Lean % corrected a little more, good fuel pressure through all ranges now, so something in that new pump they had installed was a little weak, Ran good until under load at low rpms like pulling out snd starting straight up a hill, would act like it was gonna stall for split seconds at a time, the codes coming up now were only misfire and knock sensor low circuit, I had some gm knock sensors and harness here so I decided to run a test on it. I separated the harness wires ran one to right side of engine and one across to left side. Or bank one n two. Threaded sensors into block. Reset codes drove it under all conditions I could for 3 days it runs flawlessly, so ok I know I need to change knock sensors, these are faulty. I called customer he said leave them where they are if they go bad again it’s a 20 mins swap. Tickled to death because they’ve been having trouble out of this vehicle for almost a year. And had already shot the parts cannon at it. But like I said it still had several issues when it was brought to me.

[@vicdamondjr5077]

So basically it depends on which knock sensor is bad

[@omamen5204]

i change my spark plugs an i gap 0.40 an after i got a check ingine light an mecanic say i have a bad nock censer ?

[@warrenlancaster8045]

A little late, but For a stock LS application, Copper or platinum plugs need .055-.060. Iridiums are perfect at .040.

[@hunterjustice5832]

On my truck my heater core hose broke and water went all over my engine and my knock sensors are bad would that be the reason why the knock sensors are bad

[@SoaringMech]

If the water got onto the top of the engine that could mess up the knock sensors.

[@hunterjustice5832]

sam washburn yea thats what happened thank you

[@robmccormick4403]

My friend that worked perfectly was very simple repair and now my idiot lights are off

[@T-REX72]

What if I just unplug the knock sensor and do away with it? just deal with having the code?

[@SoaringMech]

That’s is probably ok. But a lot of states won’t pass inspection with that code. I don’t know if the ecm will mess with your timing if it thinks there’s a bad sensor. If it decides to retard the timing all the time because it could be knocking, it would reduce your power and mileage. But i don’t know if it does that.

[@T-REX72]

sam washburn I like the bypass idea.

[@wesleysandifer6157]

@@SoaringMech might be worth a try. Let me know how it turns out.

[@warrenlancaster8045]

@@wesleysandifer6157 unplugging them, the ECU assumes spark knock and will pull timing enough for your gas mileage to absolutely suck. You need to tune the ECU to ignore the command from the knock sensor or fool it somehow

[@tomcooper748]

@@warrenlancaster8045 I'd love to learn how to, "...tune the ECU to ignore the command..." , can you explain that? What equipment is needed ?

[@motorizedbikesusamyrtlebea2990]

Broooooooo, thanks

[@ajgjr9962]

Why and how does water get there?? I’ve done the whole job Put the water barrier. Only to have it code up 4 months later.

[@SoaringMech]

That’s a bummer. The water gets in from splashing and condensation. Engine is hot and humid air collects under the intake manifold. Then the engine cools down and the humidity condenses onto the metal and flows to the bottom of the knock sensor wells then seeps into the threads and rusts. Eventually the this interrupts the knock sensors circuit to ground. If y0u don’t want to go through the whole replacement job again., try my solution for a few months. You can always do the full replacement in a few months.

[@digi3218]

I'm in the same boat. Pretty sure I cheaped out on the sensors though at the time not knowing any better. I assume the ACDelcos are the ones you want to buy.

[@roncon1180]

My question is how is it that there’s a bank 1 and bank 2 knock sensor when they are both mounted in between both banks and are about 4-5 inches apart. There is no way bank 1 sensor only picks up bank 1 pings and bank 2 sensor only picks up bank 2 pings. I’m not certain but I’m confident only 1 knock sensor would pick up all ping noises considering how they are mounted. Does anyone know or can confirm my theory?...I replaced both knock sensors and the harness for a bank 2 sensor failure. I think the thread on the block is rusted causing a bad ground. It’s intermittent now because it’ll only throw a pending code and then it’ll clear. It won’t store the code so the light won’t come on yet, but I’m sure it will soon if the pending code keeps coming up.

[@SoaringMech]

Good question. I asked a mechanic who was trained at the Mercedes’ factory about this and he said the second knock sensor was just for redundancy. IE. So that if one fails the working one will still get the job done. I agree with you that the mounting location means that both sensors will hear all knocks. My trucks engine has run perfectly for three years and about 20k miles on one working knock sensor with both ECM wires connected to the working sensor. I did another KZbin video explaining how to bypass a failed knock sensor on thee engines. Good luck.

[@roncon1180]

@@SoaringMech thanks for your reply. yeah I was either gonna bypass it by connecting it to bank 1 sensor or mount an exterior knock sensor on the outside. The code is gone for now but if it does come back I’ll definitely look to bypass it

[@bullofthewoods9374]

sam sadly your smarter than the GM engineer..... or for that matter all vehicle manufactures engineers. I find the newer the cars get the dumber they get! full proof of the college degree strips many of most common sense.. Im a GM nut and see more ignorant things these so called engineers design? why put the knock sensor under all the intake when there are places that are tapped on the block? one word stupid

[@Amador-u2p]

My car motor knocks if y put cheap gas but I put good stuff not hear the knocking y don't know if the stupid knock censor or the motor or the gas they put too much shiet in the carso they sell parts

[@SoaringMech]

@@Amador-u2p always use the correct octane gas. If you’re pulling a heavy load on a hot day use a higher octane for that.

[@Amador-u2p]

@@SoaringMech thanks you you ok man

[@41663]

Theres always going to be someone "knocking" a video of whatever it is whether it is the fact that they may be an all knowing mechanic with God like skills or just someone who gathers joy from arguing a point. The trick here is if it works for you then you just saved at least $300 and about 5 hours of headache or if you take it to a shop $1300 is one quote. Anyways if it dont youll know it. Take it home and start digging in its gonna be a whole lotta fun. For me it mind boggling but for alot its still a bitch to do unless your a seasoned grease monkey who knows what theyre doing

[@Dex99SS]

I wouldn't bypass both... But the LS knock sensors are within 5 inches of one another.... The official knock sensor relocation kits relocate BOTH knock sensors to the SAME PLACE on the block, literally within a half of an inch of one another. They are labeled as bank 1 and bank 2, but they are more so redundancy in pairs. 1 will do. You can scope either one, and tingy pingy the engine with the tiniest of wrenches in the front or rear, and either one can be seen on the scope "hearing" your pinging via the wrenches. Your mod to use just one is A-Okay. Absolutely no doubt about it. The only people that will tell you different are the very same people who'd jump online to tell you how to live every other aspect of your life. The "internet know it all wanna be mechanics" who can't even properly change their oil on their own, have zero actual background in electronics, mechanics, or anything else beyond reading forums and building each other up with false knowledge of which is made up on the spot and then perpetuated for years if not for ever. As a controls engineer myself who has scoped this and seen the results, who's seen GMs knock tables, and whos done the mod, believe me when I endorse this as fine and dandy to do. GM uses the two of them to reference one another. It helps to know when one is failing in a not so clear and outright blatant way (faulting to ground, not getting ground, low impedance, etc). You will lose that ability as 1 knock sensor will be referencing itself at this point, so yeah... slight risk there. But not really. No more so than driving an 00-06 truck to begin with, lol. Tell all the wanna be big brains who chime in with their "expertise" to "prove it"... and I promise you, they'll have nothing but the typical forum drivel to regurgitate back to you. "Ohhhh it won't hear the back cylinders, ohhh it won't work cuz it be bad now, Ohhh it cant put the too wire in wit duh wun wyre cuz it not cheby way do" ... okay troglodytes. . . Read a book and shut up.

[@SoaringMech]

Thanks you so much for this thoughtful and detailed explanation. I have long suspected this to be the case but did not have any way to confirm it. I did have a Mercedes trained mechanic friend who felt the same way. It’s very helpful to clarify this because so many people driving these old trucks love them, but dont have the $$ or experience to yank the manifold and replace one failed knock sensor when it isn’t necessary. Now, if they read your comment, they can bypass the bad sensor and not worry about damaging their engine. Thanks again.

[@tomcooper748]

That's interesting info Brett and soundly reinforces what Sam has been talking about for a long time. Can you explain how you scoped the knock sensor table? I'd like to learn how to do this just for fun and experience ( I'll be using H-scope).

[@shawnchildress2198]

By the way is bank 2 what's the one throwing the code this is voice text so it looks stupid that's why LOL

[@shadowopsairman1583]

Snake oil

[@tylerparker3024]

As the engine wears, it will need them. Thats the bottom line.

[@deankay4434]

It takes about 1.5 to 3 hours to change both knock sensors. They produce a constant value of A/C voltage a the PCM watches for abnormal inputs. Timing is retarded when starting, but V8 engine run 34 to 36 degrees BTDC to fire ignition. Now the octane is 87 the fuel burns fast. This is the anti-knock value. High octane burns slower and rated higher. To get the most torque and HP, they have to ignite way before TDC. Your information is wrong. Pre-detonation breaks piston ring lands, rings and at worst can bent connecting rods. Why would anyone chance this. Yes, it’s harder that an oil & filter change, but if your engine goes, cylinders get deep scratches, metal parts can bend valves, destroy the block and cylinders head. Don’t risk it! Replacement is easy; With Injectors still connected are placed to side, remove intake (Gaskets $15) wipe clean. Use a vacuum and screwdriver to clean around knock sensors, replace both ($32). Use dielectric grease on threads, torque in place, install valley pan, use high temp RED RTV to seal completely. Make connections at cam & oil pressure sensor, install new gaskets on intake, swing fuel rail, lube with silicone grease, install. Done. The time you spent looking on the internet you could have done this twice. 3 times if including effort for a video. ASE Master Tech since 78, retired (7yrs with GM as ACDelco market area service manger. L-1, P-2 certified as well.

[@SoaringMech]

@@deankay4434 thanks for the thoughtful reply. But most people watching this video have old trucks and not much money. Many are poor recent immigrants and cannot get an inspection stickers because of a bad knock sensor. On a 15 year old truck, a lot can go wrong or break when u remove the manifold and all the connections in order to get at the knock sensors, adding more cost and effort to the replacement job. Dealers charge over $1000 to do it assuming nothing goes wrong. my sons and I have driven this truck for 30k miles since I did this hack in all conditions under varying loads including towing a two ton boat 800 miles on the one good knock sensor. The engine has been flawless. Had to replace one bad injector after 28k miles. A factory trained Mercedes mechanic told me that the second knock sensor is probably redundant. IE. A single sensor will hear all knocks. After my experiment I believe him. Read some of the other comments and you will see how successful this hack has been for hundreds of people. No one has ever done it and come back with a comment saying that it damaged their engine.

[@deankay4434]

@ I know this, it is getting worse and not better. As an ASE Master at a dealer since 1978, I have seen a lot. Exhaust bolts break, they have to elongate the holes, install a flat washer and expect other problems not related to the repair, but require removal to gain access. I spent 7 years with ACDelco, holding 4hr long tech seminars for 100+ folks on 28 different subjects. Everyone did A/C systems, I did 4hrs on sensors & controls found on GM’s. Grand Blanc did not send me that book to hand out, because I created it. Best of luck to all. See ACDelco ‘tis 2 web to buy access to info and schematics plus code to program a module that belongs on a single family engine! They spend 3 months or more with every new engine that comes out in a shop writing new code if needed, but testing, inducing failures then checking for changes in the diagnostic flow charts. Been there, seen that. Have a lucky one.

[@adamhollon6035]

I’m guessing you did no research on the ecu knock sensor test procedure it doesn’t once it getting up to temp??? Lmao calm down Karen and go do your home work

[@jakepittman9818]

I disagree, you're probablly right, the ecm probablly uses a table with predetermined parameters as you mentioned. But the knock sensors are there to make up for the variables, poor fuel, extreme conditions, high density altitude (high and hot) etc. Agreed we should avoid putting low quality fuel in our vehicles, but that will inevitably happen. And the knock sensors are cheap insurance. In about 2 hours I've removed the intake manifold with all normal tools aside from a $14 fuel line removal kit. The parts (2 sensors, wiring harness and intake gaskets) was $200. It will probablly take another 2 hours to reassemble everything. So, in an afternoon and $214, I can be assured my truck will operate the way a team of highly qualified engine engineers intended.

[@SoaringMech]

It’s always best to do it the right way. Glad it has worked well so far for you. One reason many folk don’t want to pull the manifold is that there are many things to disconnect and reconnect. on a 15 year old truck its really easy to break some of these things by mistake and cause bigger problems. many people that own 15 year old trucks don’t have a lot of $$, so my solution is helpful to them. In addition, my engine has run flawlessly for two years with this fix. It never knocks because i keep it well tuned. I just replaced plugs after 50k and did an induction manifold cleaning with seafoam. Good luck.

[@BruceBanner-tm9qu]

The same highly qualified engineers who designed this crap design.....please smh you aw

[@kevinwest3689]

You need to watch your own video, you answer the question you're asking if you just listen to yourself, 1 you're not a GM engineer and you do not understand 2 if you purchased for gasoline or had a spark plug failing Etc would you rather A. broke down on the side of the road or B. Have your engine compensate for it. My advice is if you're in the woods and you have to poo, spending too much time looking for the perfect leaf, not too brittle not poison oak, it's not going to go well, sure sure one could argue you should have crap before you left the house, but you didn't have to go then, think of your knock sensor like wearing a second pair of socks, don't forget to step off the beaten path reverse roll and don't litter, only you can prevent a slippery Trail.

[@SoaringMech]

That was deep

[@henryrobinson9837]

put an oscilloscope on both sensors and you can answer a lot of your questions about the operation and function of knock sensors, if you dont use an oscilloscope you have no authority or expertise in guiding people in auto repair, i worked at dealership for 30+ years

[@SoaringMech]

Henry, I know you mean well, but the DIY community exists because so many dealers overcharge customers, especially women. So we share information and do the best we can with limited amounts of money. Instead of criticizing, please share the enormous knowledge you built up over thirty years. Telling us to get oscilloscopes just isn’t all that helpful. I’m sure you know a lot about what the ecm does with the knock sensor inputs. Please share that.

[@henryrobinson9837]

@@SoaringMech GM paid engineers millions of dollars to design it a certain way ,telling people to bypass sensors is not in the layman's best interest.

[@petripat5979]

@@SoaringMech Thanks for the wisdom

[@catmanzrt]

@@henryrobinson9837 You would think those million dollar engineers could have come up with a design that doesn't fill with standing water causing severe rust and premature failure resulting in a thousand dollar repair. Screw GM. I'm done with them.

[@theamerican7080]

Wow. Helps nobody but the shop equipped with a scope.