This Is All New To Me!! Cutting Open A Knock Sensor. 2004 Silverado 6.0
Вставка
- Опубліковано 24 жов 2024
- Cyclops Light - amzn.to/48BiJbG
Easy to use handheld - amzn.to/46nMFrz
Budget friendly, professional style scanner - amzn.to/44iDdUM
Basic Code Reader - amzn.to/3GZFDhT
Blue tooth scan tool - amzn.to/3org3vL
Perfect panel trim tool - amzn.to/40hPshS
Push pin removal pliers - amzn.to/3US2FN7
Excellent beginner plus tool kit - amzn.to/3UY6e4z
Excellent Basic Starter Tool Kit - amzn.to/41JVRn2
Must Have Gearwrench set - amzn.to/3AfZNAc
Power Probe Circuit Tester - amzn.to/3mOrQ6N
Basic Test Light - amzn.to/40mKdNN
#misfire #checkenginelight #checkengine #knocksensor #ls #lsmotor #gmtruck
Facebook links - both Facebook are closed groups, meaning you have to answer all the questions to join. Both groups are full of fellow mechanics, some retired, some working in the trade & some excellent backyard/shade tree mechanics.
Show us what you're working on!
Wrenching with Kenny = / 575412787264269
Backyard Mechanics = / 442507346633755
@WrenchingWithKenny @SNAFU.performance @traditionovertrend2704 @ktmracingsisters1261 @matersworkshop6123 @MotorMouthRadio @cruzcorp914
#wrenchingwithkenny #keepwrenching #wesselmotorworks
#mechanic #automechanic #autorepair #automotiverepair
This particular Knock sensor works like this: You essentially have two resistors in parallel. The little resistor soldered in and the connection that runs through the spring, through the piezoelectric crystal and then the outer shell. When you vibrate the crystal, it generates a small amount of voltage which then changes the overall resistance of the knock sensor.
I think the computer in your car reads the voltage from the piezoelectric crystal, possibly across that resistor.
I admit I am not an automotive mechanic, but I am a ticketed Industrial Instrument Mechanic and worked with all kinds of computers and PLCs. Computers usually want to see voltage, even if a variable or static resistance is what is creating the voltage.
In this case I think it is simply the voltage generated by the crystal and ground is the other side of the resistor.
@@rickschlosser6793yep, essentially a microphone... Computer "listens" for the waveform generated by detonation; two flame fronts colliding. Kia's and Hyundai's also got reprogrammed to listen for the waveform generated by failing bottom end bearings...
Piezoelectric crystals create a voltage when mechanically stressed. The spring and resistors provide electrical contact with the crystal, and parallel resistance so the ECM knows it's connected and probably to limit voltage as well. Very simple, but effective. That same crystal element can also be found in things like alarm clocks in place of a speaker, because piezo crystals also mechanically deform when voltage is applied. They don't make much sound on their own, but if stuck to a larger surface can produce a decent amount of sound. As a kid I used to freak out my siblings by using a piezo disk from an alarm clock taped to the outside of their bedroom window down in the corner, very hard to see, and some thin wires running to a tape recorder in my room. I would record scratching and tapping sounds, and whispered voices saying things like, "Let me innnnn....", and I would transmit them to the window. A very effective prank! I would hit the play button, and a few minutes later there would be pandemonium. I know, I'm a bad boy. In my defense, I was young, and for some reason this was amusing.
I'm over 30 and still find this amusing
Very creative!
@@TRiToN219 I'm more than twice your age and I still find it amusing. Easily amused or always a kid inside?
In this application, the piezoelectric crystal is being used as an incredibly sensitive yet robust microphone. The ECU is looking for a particular "pitch" or frequency being picked up by the vibration of the crystal to determine if the engine is knocking. The crystal actually gives off a tiny AC voltage when vibrated and because the voltage is so small, the 100K resistor is placed across it to help "shunt" any noise that may be present in the wire leading back to the ECU, this is because the impedance (resistance) is almost infinite and allows interference voltages to appear. Think along the lines of the CAN buss terminating resistors, same deal. The crystal itself should read open circuit under normal conditions. The reason your ohm meter fluctuated was because the tiny AC voltage made when struck superimposed itself on top of the 9 volts DC present at the meter probes when in resistance measuring mode. Try tapping one with the meter set to AC millivolts. If you have access to any basic oscilloscope, you could observe the wave on the screen when tapping it. There is no "correct" waveform as suck but you do want to see an output from it.
Piezo crystals are used in the audio world commonly, they can be used as a microphone, a phonograph pickup, acoustic guitar pickup, or as a high frequency horn speaker "tweeter". Piezo crystals have this interesting property that when mechanically vibrated, they give off voltage, or if an AC voltage is applied to it, it will vibrate to produce sound. An extreme example of the former is the igniter in your gas BBQ or stove, its a piezo crystal that is rapidly struck to give off a very large voltage that makes the spark to light the gas.
The white centre is the element. The resistor is there to bleed voltage away. The sensor develops a voltage when vibrated, and the spring transfers it to the connector, and then to the ECU. The ECU will show knock, measuring the voltage developed by the sensor, reading up to 30V on the sensor for severe knock, and then adjusting to reduce it. The spring is the connection so it allows the disk to flex, as it is held in place only by the edge, and under it is a small hollow area so the brass disk can bend with the vibration, like a speaker cone. Exact same disk as is used in musical cards, held at the edge, and the voltage applied makes it flex, and produce a sound, but in reverse, the flex making a voltage. Resistor is there to bleed off DC voltage, and also so the ECU can tell the sensor is there, as the ECU applies 5V via a similar value resistor, and measures the DC voltage on the wire, to see the sensor is there, and the wire is not shorted or open. The signal is strong enough that the resistor does not interfere, you can test them with the tapping, after checking resistance is correct, by putting the meter into AC volt mode, selecting the 30VAC mode (as otherwise the meter autorange will make it display all over the place) and tapping it, where a good sensor should develop anything from 5 to 30VAC signal on impact, depending on where you tap, and also how it is held. Some of the sensors ( VW being one, but all that use a bolt through the centre are the same) are very sensitive to the bolt being the correct torque, too little and they do not work well, and too tight and the ceramic material breaks inside the housing, generating low or erratic output.
Piezo crystals are totally magic, they are a special compound with different metals that are baked at over 3000degC. They work like a capacitor, that changes value according to how much it is compressed. Imagine a capacitor where you all of a sudden doubles the capacitance, the voltage across it will then halve, since the charge is still the same. When you use the ohm setting on the multimeter, it puts a tiny voltage across the device, and when you bang on it, it changes capacitance, and the voltage fluctuates. This gives the nervous ohm reading. Nice video 👍
The piezo is the white disc in the bottom. When it gets a sudden impact, it produces a voltage spike, both + and -. It is an AC voltage. The resistor is to discharge any static voltage on the piezo and tell the computer that something is hooked up. The piezo is that same as many beepers used to make a sound. If they are driven with an AC current they'll make a sound. If an acoustic sound is applied they will make a voltage. This is just like a coil of wire in a magnetic field if it moves, it generates a voltage while moving, If a voltage is applied to them, it will make the coil want to move. The difference is the piezo is more like a capacitor than a coil. the current only flows momentarily, either when struck or when a voltage is applied. There are piezo crystals like quartz crystals but the sensor has no a crystal. The disk is made with two conductors, on either side and a piece of special ceramic that holds an internal charge in the ceramic, by aligning an electric field, when it cured. It is a special ceramic that make a strong piezo device.
Even when not pinging, the running engine makes some voltage. When there is pinging, the AC voltage is a lot stronger. I'm to totally sure but I suspect the spring rings some from a ping and prolongs the AC voltage, as well as conducting electrical signal to the connector. If you want to see it work, you'd need to use an oscilloscope. The reaction of the ohm meter doesn't show the entire response well since it is too slow and only flickers when struck. It would show much clearer on an oscilloscope.
It works like the push button that lights your grill. The snap you hear when you push the button is a little hammer that physically strikes a piezoelectric crystal. When the crystal is physically struck, it creates a voltage. In the case of your grill, that voltage is high enough to make a spark that lights the gas.
The sensor works the same way - the knock is the 'hammer' that physically shocks the crystal and produces a voltage. The voltage is limited by the resistor to a value low enough that it won't destroy the ECU, but high enough that the ECU can sense it.
The mind of man is amazing.
Watching this and reading the comments It has helped me to understand the knock sensor like never before Very good video!
Seriously!!!
Taking components apart is a great way on learning how to fix them.
I once had a window motor on a used car, that was either damaged or had been taken apart prior, where the rotor of the electric motor would not engage the gear for the window.
Fortunately, I had some spare parts and hardware and was able to fix it and get the window working again without having to replace the motor.
Another Ivan!
That looks exactly like the piezoelectric beeper in some watches. Its been around forever and very reliable. You know that's the same quartz crystal that powers the click-to-light lighters? Very fricking cool! Thank you Kenny!
Obviously Kenny, you opened up a can of worms here !!! I was so excited to read that so many of your viewers, came from so many trade disciplines, and had so much to offer on the science behind the crystals function!!! 🙂 I am that kid, who took things apart, from 5 or 6 years old.. And yes, at 9, 10 or so, used my "knowledge" for pranks on siblings as well.. Hidden speakers, hooked to tape decks, ran wires to their TV's in their rooms, hooked to DC motors, so I could randomly scramble the reception during pro hockey games on UHF !!!!
Good times....
LoL 🤣 o
We removed the microphone from a telephone. Hooked up the phone to our line. We could listen in without being heard.
That disk in the bottom of both of the first two sensors *IS* the piezoelectric disk. The spring is one of the contacts, and if it has any corrosion, it will give trouble.
Also, you’ll want to use the mV setting on the meter to test for whether it’s good.
A.S. Electronics, 1984.
A piezo acts essentially like a microphone, you can see the piezo crystal mounted to the base of the sensor so that it makes solid mechanical connection to the block. The electronics monitor the AC signal from the sensor for spikes of a certain frequency and the timing of those spikes within the cycle of the engine to determine if the engine is knocking.
The white disk under the spring is likely the peizo element. It creates an electrical charge when it flexes. The same device is also used as a speaker in the musical greeting cards, because they also generate a vibration when a voltage is applied
Thanks Kenny. This was really interesting! I learnt something today.
These crystals are also used in those 'click start' cigarette lighters. That 'Click' is a little spring loaded hammer hitting the crystal which generates a spark.
Thanks for the demo. FYI - The Ceiling Fans need oil!
Yes,I will tell you how it works,I did a module at tech as an electrician called basic transducers which is what a knock sensor is,a piezoelectric transducer, it's an active transducer,not a passive one such as a coolant temperature sensor.
A small voltage is generated by the piezo crystal whenever a knock occurs which voltage is sent back to the PCM which in turn retards the timing within the PCM, so it works the same as the piezo ignitor does on your gas barbeque.
I have found that the cheap ones are fake & are epoxy filled because I kept getting a check engine symbol in my 5.7 litre Chevrolet LS1 V8 powered Holden VY SS Commodore which is Australian built by Holden.
Once the coolant temperature reaches 70°C the engine doesn't receive any signal from the knock sensor when it's expected then a knock sensor code such as a P0332 which is a low output code from the rear knock sensor in my case was found when I bought a scan tool which can read the proprietary SAE J1850 VPW codes, the cheap $50 AUD scan tool could read codes in my dads newer 2013 model Holden (Chevrolet) Colorado which has the Newer CAN OBD2 ISO15765 compliant engine management system but that scan tool couldn't read the codes in my Commodore,so I bought a $200 AUD Bosch scan tool which does.
I have used the U.S. made Wells branded knock sensors as well as replacing the knock sensor wiring harness as well & I haven't had any problems with my car for the last 5 years, keep pressure cleaners away from that engine as well because water just sits inside of the knock sensor wells & corrodes them out.
Here's another video regarding fake knock sensors in the LS or Vortec engines, note that the 5.3 litre V8 engine was also bolted into a Chevrolet Impala as well !
ua-cam.com/video/Xavg9IqvBvA/v-deo.htmlsi=OAYhtjbN7eyydJT9
When you're paying attention, you can always learn EXTRA little tidbits watching Kenny's videos.
Today I learned you can make a workbench out of pure dirt.
stretch the spring out so it puts more pressure on the piezo element
GM tech school told us a loose trailer hitch caused pick up to run erratic on level ground, but ran fine on up or down grade. Timing was changing to adjust for knock.
Good Afternoon Kenny. I’m a commercial aircraft mechanic. Modern jet engines use piezoelectric crystals in vibration sensors to detect rotor imbalance. It’s been my understanding that these sensors generate electricity when agitated by pressure or vibration. The resistor installed in yours would presumably be a filter for stray voltages. I’d be curious if you find out otherwise.
You are actually measuring a voltage. The resistor is there probably to dampen voltage spikes. The crystal generates a high voltage similar to a butane barbecue lighter. You pull the trigger and a hammer hits the piezo crystal generating a high voltage spark to light the butane. Same situation with the knock sensor, tap the threaded end and you generate a voltage spike which is dampened by the resistor to a safe value for the ecm/bcm to read. If the resistor has a color code the value should be close to what you measured. The function of the resistor is similar to the resistor connected across a relay coil to dampen the back emf when the coil is open circuited. Piezo operation same as the old crystal phono cartridges. Wiggle the needle and you generate a voltage that is the amplified to produce music.
Congratulations on passing 100,000 subscribers!!
The push button igniter on your torch and BBQ grill are pizzo. The wack of the button hitting the crystal creates the spark.
IOW the crystal creates voltage, and this is what the ecu is looking for
I am with you Kenny, I have no idea how they really work. I need to research 👍
Thanks Kenny! New to me for sure!
Piezoelectric makes the sneakers light up! 😂
Yes Kenny that was very interesting to me because I used to work on my own vehicles before they started becoming complicated with all of the computer junk that they started putting on them
I think that the spring touching the "wafer" as you called it, changes the resistance when it knocks. The amount of the resistance changes by the amount of movement of the crystals and the vibration in the spring. That's my take on it, I could be wrong. It gives me ideas though on old cars that need knock sensors, instead of going through all the work to mount them under the intake, just unplug them and mount the new ones somewhere on the block. Thanks for the video, interesting.
Same principal used in propane grill & oven burner starters
My guess is that the resistor serves two functions. It provides a method of DC biasing the sensor signal to a level where the sensor signal is always positive. It would have the added benefit of allowing the PCM to detect a missing sensor. The actual piezo element generates a small AC signal that is superimposed on the DC bias. This combined sigmal is processed by the PCM. It would be interesting to set the meter to AC voltage and do the tapping.
The Piezo Effect is is taking mechanical motion (knocking/vibration) and generating electricty. Just like the click ignitor for your gas grill. It uses a ceramic or quartz crystal. The crystal structure is the magic part. Since it is a rock, it is also a pretty good insulator. AKA infinite resistance, or open circuit
The resistor is there to make a DC electrical path. This way the ECU knows it is plugged in. The resistor value is high enough so it does not load down the voltage generated by the crystal.
Notice, how when you bang on it the resistance increased. The little bit of voltage generated faked out the measurement circuit of the meter making it read a higher resistance.
As an experiment, I am guessing if you reversed the meter leads the resistance will jump to a lower value because the voltage generated is now opposite to that the meter is applying.(1)
(1) Take 2 meters. Connect the leads together. Set one to Ohms, the other to DC Volts. Have fun
A scope would be the thing to look at the sensor signal with. Look at a known good sensor on a running engine, then hook the scope up to your test sensor and tap on it with the wrench. I think a person will see that both the max voltage and the shape of the signal will change when knock is detected. The ECM could be looking at either property or both.
That was a very interesting test. Thank you for showing this on video.
Great Video Kenny!
It’s all about that base…
😅. I couldn’t resist.
Kenny, in addition to the comments I saw, I have read that the sensor produces a frequency or Hz output that the ECM receives. If I recall correctly it is around 4000 Hz or 4K Hz when the knocking starts. So, I believe it is the frequency that the ECM uses to determine the engine is knocking. I don’t have a scope soI never actually looked at it but that is how vibration sensors work.
remember if you scope these the scope reads voltage over time
They are ls and was first designed by mercury outboards in Stillwater Oklahoma for GM and started life as 5.7 in 1998
Source?
Google did mercury in Stillwater go into go into partnership in designing the ls engine came up for me
works like a crystal watch .
Piezoelectric means they generate an electrical signal when vibrated at a specific frequency or when squeezed. They are not resistive elements. You should test them with a scope.
Hi Kenny ,great video reminded me how I had a car in the shop with bad fuel consumption checked all the usual things couldn’t come up with a reason in the end found the timing retarded when I removed the knock sensor the timing advanced considerably also noticed a hydraulic lifter was tapping louder than normal replaced the noisy lifter refitted the knock sensor checked the timing everything back to normal so the noisy lifter was causing the knock sensor to activate and retard the engine timing causing bad fuel consumption customer very happy regards peta australia
Interesting!! Makes sense!
Lesson is OEM only on engine sensors! That's my policy. They create voltage when compressed turn the meter to voltage
Some people just never learn this!
@182QKFTW been turning wrenches 20+ years and I still haven't learned this 😂
Hell just about every sensor on my 7.3 powerstroke has been replaced with aftermarket ones and they've all been working fine for years. I'll be at 400,000 miles in just a matter of weeks on the old girl!
If it's a customers vehicle tho, I usually try to stick with OEM unless their on a tight budget. Really only been burned by aftermarket MAF sensors that give wacky readings if I'm being honest tho
Since it produces a tiny amount of current, it should be measured with the voltmeter scale on your DVOM. Try that I would be curious
thanks, great stuff.. ( research on a greasy, well-used workbench..)
Use the AC voltage function to see if the sensor is good. Piezo electric crystals generate voltage and very little current.
If you measure ohm across the crystal itself I suspect it will be open or very high. the 100k resistor is probably utilized to create a static signal the ecu can detect.
THANK YOU !
The piezoelectric crystal does not change its resistance that much, but when mechanically impacted it produces voltage. And quite a lot of voltage. If you have ever used a lighter with a piezoelectric crystal, you know that even a small blow on it produces enough voltage to form a fairly significant spark. Judging by the shape of the plate inside this sensor, its crystal is, of course, not the same as that of a lighter, but in essence it is a piezoelectric microphone. But the principle is the same.
I thought you were gonna find some Oompa Loompas in there.
piezo crystal devices actually generate a milli-volt pulse. yes when measuring ohms the meter is applying its own voltage.. so as you strike the crystal the meter sees a change in V. Yes.. the Crystal is the white disk on the bottom of the sensor
Tariq Lab used a piezoelectric crystal to power an LED.
Next time you replace a fuel pump, cut the old one open. I'm sure many people haven't seen the insides. They probably don't know that gas flows through the motor to cool it.
The spring picks up vibration and touches the piezo which changes resistance
Some of the Japanese cars knock sensors get interesting when you take them apart.
Replaced one recently on an Audi which solved the problem of poor acceleration in the car so I dont know if it was giving a false reading or what. Surely, if a car is running properly, a dud knock sensor wouldn't have any input.
If I ever owned a 5.3 with knock sensors that went bad I would mount them to the out side of the block and run the harness from the back to the new location .
Just use OEM sensors and never wash one of these engines. Or buy a 2007 or later....but that opens up a whole new can of worms! Cylinder deactivation
The spring is just a contact point of connection.
Is that spring tuned to a specific frequency?
Voltage not ohms is produced. "I hear you knocking but you can't come in"
Do soap dispensers have piezoelectric crystals to make the soap solution foam when voltage is applied to the crystals they vibrate? So it would probably stand to reason that vibrations will make the crystal generate some small amount of voltage?
I think the failure is a matter of are the crystals broken or not able to vibrate and that’s why the knock sensor is failing.
Ooooooooo, Fluke!
You must be rich!!!
Piezo crystals generate a voltage
They found them at Roswell 🛸🛸🛸
Piezoelectric crystals were widely used as cheap audio microphones in low cost Audio devices . If you think of a knock sensor as a microphone listening for detonation sounds , you'll be on the right track. They pick up those sounds , convert it to a voltage that they send to the ECU , which reads that as a signal to back off the timing advance until the sounds go away. The ECU defaults to an amount of timing advance which is higher than needed and adjusts backward from there ... until the sensors fail and the default timing becomes less advanced ( or put another way , more retarded ). Sort of a "limp mode" . This causes the power loss until the sensors are replaced .
Knock Knock! Whos there? Cargo,,,,,Cargo Who? Cargo better if you fill it with gas first!!!LOL
The pieso is on the bottom half
Is it a piezo device?
Its not based on resistance they generate voltage based on the vibration of the crystals
Ask scanner Danner??
Does anyone make a knock sensor for my 1970 396 Chevy engine?
Yeah high test non ethanol gas! 😂
😂😂
pezo effect. is electric .. when the pezo is moved it will make lil bits of electric. as far as i remember
I learned that the pressure exerted on the crystals creates electricity.. roughly translated.
They produce AC voltage from the crystals somehow
Not identical. LSx is aluminum block performance oriented car motor. Numerous differences in the way the block is designed.
switch to m volts
Piezoelectricity
Piezoelectricity is the electric charge that accumulates in certain solid materials-such as crystals, certain ceramics, and biological matter such as bone, DNA, and various proteins-in response to applied mechanical stress. The word piezoelectricity means electricity resulting from pressure and latent heat. Wikipedia
Or check resistor it's bad in ohns
I don’t need knock sensors on my car because I use premium gasoline.
What car?
Interesting video on knock sensors here: ua-cam.com/video/MCCNXziUj8k/v-deo.htmlsi=LWNHhsBaUHuZ4BYJ
Life is too short not to use oem sensors. When you use aftermarket sensors there is a good chance that you will be doing the job on your own dime
Kenny ground spring to the base, it's got act in manner of vibration like earth quake does to meter they use, can't think of its name, sends signal to current back vehicles computer to adjust timing
Ummmm good morning Mr Kenny, hope y'all have a wonderful day. 🎉 Well now you did it 😅, I'll be looking up Crank sensors for the rest of the day 😅. Think I'll need cheeseburgers to keep me going 😅😂🎉
The actual sensor part is that round disk of pizoelectric wafer that the spring touches. The resister is just a resistive termination. The meter should be on micro or pico volts to see the tiny voltage created by vibration of the pizo disk. The output is a tiny voltage and not resistive.
I think they convert mechanical force into small blip of voltage.