Automotive Vibration Analyzers – Part 4 of 5 – GM PicoScope NHV

Automotive Vibration Analyzers – Part 4 of 5 – GM PicoScope NHV


this video is part 4 of a five part series on automotive vibration analyzers in this episode we will cover the Pico scope NVH diagnostic kit for General Motors dealerships part number c18145 t now even though this says GM on it it actually could be used on other vehicles and I’ll explain that a little bit later inside of this kit we have a four channel automotive Pico scope we have four scope channels here and we’re going to be using channel be here for the vibration interface the NVH interface box that comes in this kit and the pico scope if you’re familiar with them is a USB interface module to a laptop computer running Microsoft Windows so to diagnose vibrations using the Pico scope nbh kit we need the appropriate Pico scope oscilloscope interface here and there’s several of those different models to channel 4 channel that are supported by this particular one I think it’s a 44 24 comes in this kit has a maximum of plus or minus 100 volts peak so not only can this be used as an a vibration diagnostic tool but this can be used as a four channel oscilloscope for electrical diagnosis so it’s a it’s a very cool setup so we’re gonna need the Pico scope interface I’ll set that over here we’ll need the nbh interface and then also we have a vibration sensor an accelerometer and I’ve got a washer stuck to the end of that to keep the magnet strong I’ll leave that on there for now the magnet screws on to the end of the sensor and it has arrows on it as you can may be able to see they’re indicating up and down and so according to Pico they want you to mount this sensor to where it’s either pointing up or down wherever you’ve got it mounted magnetically we’ll do some experiments and see if it really matters if it’s up or down for vibration diagnosis I’m not sure that it does I’m not sure I believe that I think the frequency will still be picked up for the vibration possibly the amplitude will be different but we’ll find out I’ve got a 2013 Camaro zl1 over here that I’ve installed some vibration bugs on my vehicle and we’re going to take this over and try it out and we’ll try the sensor in a few different positions and see if it’s if it makes any difference okay so the vibration sensor is going to connect to the interface box and then the interface box connects to the oscilloscope interface and then the oscilloscope connects to a laptop so for just regular vibration diagnosis these are the some of the parts we need and then inside of this lid it swings open and there’s some more parts in this diagnostic kit we have a USB cable that we’ll need for the Pico scope interface USB and then it has two long scope leads in it with the the same connector on either end and this is to connect the Pico scope to the NVH interface and so there’s two of those we only need one for vibration diagnosis the other one in this upper part of the kit it has an optical sensor interface and it has an optical sensor right here with a magnetic base mount and this is used for driveline vibration or I’m sorry yet balancing drive lines and that’s what this other cable is for is to connect to the interface for the optical sensor but for now we’re going to pass on the propeller shaft vibration correction and balancing and I will probably do a separate video on that I still need to do a video for the balancing prop shafts with the EBA but maybe I’ll do both in the same no I’ll do two separate videos anyway so for what we need to diagnose vibrations on a car in this kit once again we’ve got we’ve got to have and let me bring it over here a laptop computer running Windows and for the general motors version of this their special general motors software that you can download from the GM dealer solutions website but you have to have a GM login to be able to do that I told you earlier that this kit could work on other vehicles and Pico scope has some generic software it is called Piko automotive diagnostic software if you go to their website pico Auto dot-com you can download the software for free and then even though the says GM this same setup would work on another vehicle okay so to get this working we need the laptop we need to have two USB ports at bare minimum so we’re going to take the USB cable that came with the kit we’re going to plug it in to the Pico scope interface scope interface box here so I’ll plug that in to the laptop and it has a driver that comes with the Pico software to enable the computer to read from the oscilloscope and then we’ll take our scope lead here and we’ll attach it to channel B of the 4 channel scope or channel B of a two channel scope and then we will attach that to the nbh interface and then we’ll take the vibration sensor and it’s keyed so it has to plug in one way only we’ll plug that in to the NVH interface and it has a threaded fitting to hold it in place when you get that plugged in and it’s operating properly there’s a LED on the end here that’ll blink periodically to let you know that the NVH interface box is working if you don’t see that blinking there’s an internal battery in here and you take these screws out and replace that battery ok so now this is the vibration analyzer and in the first three episodes of this five-part series on vibration analyzers we looked at a Stratton Sairam être we looked at the Fram resonant Reed tachometer we looked at the electronic vibration analyzer in the four different versions of that all of those do well this set up here from Pico scope does what all of those do it measures vibration frequencies and amplitudes so this is a much more sensitive sensor than the Eva had it’s much more sensitive than the Reed tachometer or the sairam etre I really like this sensor it’s got a very strong magnet on it though so whenever you stick it to something on the car make sure you’re hanging on to the housing here when you take it off rather than pulling on the cable because I’m sure over time that’s going to cause the cable to break loose okay so that’s the vibration analyzer portion of the Pico scope kit but that’s not all if you recall from the electronic vibration analyzer episode that I did I told you that we needed vibration frequency and amplitude but we also need engine rpm and so what Pico has done is what I think is a very smart thing to do they have configured their software to work with a the J 2534 data link connector interface it’s a kind of a generic interface to communicate with onboard engine control modules and for general motors the interface that GM uses is called the MDI the multiple diagnostic interface and the MDI just simply has a long skinny USB cable but I’m going to plug in to the laptop and then on the other end of the MDI we have a 16 pin data link connector and we’re going to plug that into the car and the Pico sculpt software will automatically communicate with the car pull the VIN number decide what engine it is and how to communicate with it and read the engine rpm automatically now the beauty of this is we’ve got the engine rpm we’ve got the vibration frequency and if you recall from the vibrate software demonstration I showed you in the second episode the last half of the second episode those are the two parameters we need to nail down or narrow down the group of rotating parts on the car that is responsible for the vibration that you’re trying to diagnose so I think they’ve done a really good job in episode 5 I’ll show you the generic kit that they make for independent shops this once again this is a specific kit for General Motors as General Motors specific software and help file and so on and I’m sure they’re working on packages for other automobile manufacturers too but there’s a generic package out there that would work with just about anybody’s vehicle as long as it had the 16 pin data link connector and supported the J 2534 communication interface all right so let’s let’s open up the software here what we can’t yet we have to connect it to the vehicle so I’m going to take this over to the vehicle and we will connect it up and show you the software and then do some Diagnostics on the vehicle okay we’re over to the 2013 Camaro zl1 that we have here to experiment on I’ve installed some vibration problems on this car and we are going to use the GM version of the Pico scope software to diagnose the vibration problems on this car and so as I mentioned over at the other bench we’ve got a USB connection that hooks the Pico scope oscilloscope box to the laptop and then the scope lead cable that connects the NVH interface to the oscilloscope and then the vibration sensor itself we’ve got mounted inside the car we open the door let’s look at where that sensor is so we’ve got it mounted on the seat frame right in front of the seat looks like we’re not going to be able to see it very well but anyway it sits right there in front of the seat on the steel seat frame go ahead and shut the door there and we’ve got a good solid magnetic mount for the sensor it just happens to be sitting in the vertical position which is how Pico scope recommends that we connect it and so now let’s let’s take a look at the the software here on the computer okay so I’ve just got a shortcut for the software right down here I’m gonna click on that it’s just labeled GM NVH brings up this screen here and over here on the left hand side we have an option that reads in VH or we have an option that’s reads balancing we’re not gonna do balancing in this episode we’ll we’ll do another one on balancing so we’re just going to go with NVH so I’ll click on that and up pops the Pico scope NVH analyzer setup wizard and we’re gonna select start a new test we could also load a saved test if we had saved any previous diagnostic processes and we could skip the wizard and just use the last settings so if we’d already punched in this vehicle it remembers the last vehicle and we could go to there to just instantly start again on the same car but we’re gonna go with start a new test so when we start a new test it brings up a a window here and it has engine RPMs selection at the top here and what it wants us to do is select one of three ways for the oscilloscope software the Pico scope software to determine engine rpm one way is to use the data link connector so we right now it has selected the GM MDI or and approved J 2534 device J 2534 is a Society of Automotive Engineers standard for data communication so we were telling it to select or search the J 2534 because the GM MDI supports that we could also tell it to search for an elm327 interface now let me zoom the camera out here a little bit and show you I have personally tried right on this this same vehicle a couple of other interface methods besides the GM MDI now there’s a new MDI coming out it’s the MDI to so that the old MDI will become a little more plentiful but it is a fairly expensive piece of equipment I have here that I just ordered off of the Internet I can’t remember I believe it was on Amazon but this is a elm327 USB data link connector interface and I believe it was around $30 the GM MDI is a lot more expensive than that but the GM MDI does a whole lot more than this Elm will do but the Elm will work for the NVH diagnostic so if you get a Elm USB interface and you can use that with the GM software at least that I’ve I’ve found so far also there’s another company called Mongoose this is the Mongoose Pro MFC from Drew technologies and it also works of course both the Elm and the the Mongoose you have to install the USB drivers for them to work but both of these I tried on this Camaro just before shooting this video and they work just fine what does not work and don’t get tricked into buying any of these are the wireless interfaces that say elm327 arm there’s a there’s a Bluetooth interface one there’s a Wi-Fi interfaced one and then there’s a small newer version 2.1 bluetooth interface none of these work with the current Piko scope software who knows they may in the future that way there’s no wire between the data link connector and the laptop while you’re doing diagnosis but none of these work at the moment so this is the GM software we’re supposed to use the GM MDI with it what’s your fear at a dealership you have at least one but if you’re doing NVH diagnosis and you don’t have another MDI rather than spending all that extra money on one just get one of these less expensive ones the Mongoose ones are around four or five hundred dollars somewhere in that range and there’s different Mongoose versions for different vehicle manufacturers that do more than just your generic J 2534 communication okay the other option is channel a it says square wave tachometer some European cars so if you’re doing this in Europe I forget which pin it is maybe it’s pin one of the data link connector over there with the diesel engines is just simply a tachometer signal and so you could pick it up there off of that or there’s another option here that says reads static and that static rpm and that’s to where you don’t have to have an interface with a data link connector you just simply punch in the engine rpm while or that the engine is at while the vibration is occurring and it’ll base its calculations on that so we’re going to hit next it’s going to try to connect with the MDI and the MDI will try to connect with the vehicle and let me zoom in so you can see what it says here it says the MDI is connected it’s pulled the VIN number up for this particular vehicle so I’m going to hit next now we have to tell it what type of engine is that a V type engine or an inline engine and how many cylinders we need to know that because there are different types of normal vibrations for different configurations of engines and we need we need to determine if it’s a normal vibration then we have a power train mount problem a motor mount trans mount exhaust amount that’s transferring the vibration into the passenger compartment if it’s a non normal vibration then we try to fix the source of the vibration rather than fix the transfer path so we’ll hit next to continue want to know is that rear wheel drive front-wheel drive all wheel drive or four-wheel drive we’re going to go with rear-wheel drive on this Camaro we need to know the rear differential gear ratio now in a General Motors vehicle that’s the RPO code the regular production option code typically on the Camaro that would begin with the letter G but it could be an H it could be a F also but there’s a three-digit code that you look up on the car on an RPO sticker and then you compare that to code to GM service information to get the gear ratio and you enter that in here this cars a 323 luckily it’s printed right on a sticker on the bottom of the rear differentials so I looked out on this one so I’ll hit next then they want us to enter the tire sizes this car has two 8535 our 20 and actually their zr 20s but only an enter the z it just once they are and we’re gonna use the same value for both tires so we’ll hit next to continue we want to know where the sensor is located we have the passenger compartment or the engine compartment as an option and which sensor it defaults to the TA 183 sensor that comes with the Pico scope kit but there are other sensors available also so we’ll hit next and it tells us to connect the accelerometer SEC accelerometer to channel B of the oscilloscope tap on the sensor to verify the signal we just kind of wiggle the sensor a little bit there and as he bumped at the spike went over we’re getting we’re getting a signal quality here a signal if there was no signal at all then it’s not connected maybe you’ve got a dead battery in the NVH interface box so we’ll hit next tells us to attach the accelerometer in the upright position that on the driver’s seat rail that’s the best play that’s the best place for the sensor in my 20 years of vibration diagnosis experience the the thing you’re trying to do is duplicate what the customer or the driver of the vehicle is is complaining of and it needs to be there in the passenger compartment I have never found a vehicle that I could not find the source of the vibration with the sensor in the right there on the driver seat rail this the sensor location will affect the amplitude level which is how hard it’s shaking and this software will measure the amplitude level but the frequency will be the same and it’s the it’s really the frequency that we’re matching to the different rotating components so we will hit next it says you have completed the setup process and now can perform NVH tests click here for help on diagnosing the NVH faults if you need some help you click on that and it opens up the vibrate software help file for diagnostics and it has all kinds of great step-by-step information in there on narrowing down the source of the vibration and repairing it but you can’t even do that yet until you figure out which group of rotating parts on the car is responsible for the vibration and typically there are three groups you’ve got things that rotate the same speed as the engine or rotate relative to engine speed so those are called the engine speed related by versions there are components that spin the same speed as the tire tire and will assembly so all of those and then you have things that spin the same speed as the propeller shaft so those are the three main groups of parts that can cause a vibration on a vehicle there are electric motor driven components too but those are a little easier to diagnose since you can turn those things on and off okay so right now we’re looking at the screen nothing’s going on we’re gonna hit start recording down here we can click it with the mouse or we can just hit the spacebar to start recording and we have several different options to display what the Pico scope software thinks is the source of the vibration on the vehicle right now we’re looking at bar graph and between bar graph and frequency those two I think are the most helpful out of these three and we’re going to look at both of them so let’s go ahead and start the engine and just let it idle as you can see here on the screen the blue line represents engine rpm the black line represents the vibrations that the sensor is picking up now we’re just in park with the engine idling this is a brand new car so we would hope there would be no abnormal vibrations now let’s look at the bar graph there’s barely anything going on up here we have an e1 which is first-order engine vibration which means there’s one shake per revolution of the crankshaft we also have an e4 which is four shakes per revolution of the crankshaft now e4 is one of those normal vibrations because it’s an 8 cylinder engine four cylinders fire per revolution of the crankshaft so you’ve got the thrust of the compression stroke pushing down on the crankshaft and you get four pulsations per revolution but it should be really low in amplitude and this one is what they tell us in the GM specifications is we want to keep the vibration amplitude below 10 millage ease and the G over here forces the G is a force of gravity’s so we’ve got a tiny bit of efore showing up and that’s because it’s a normal vibration but it’s a extremely small amount of amplitude well within specification if this were a diesel it would be a little higher because the diesels have higher compression ratios and their pulsations are a little more severe but we also have listed across the screen we have t1 t2 t3 those are first-order second-order and third-order tire speed related vibrations right now the vehicle is stopped so the tires aren’t even rotating over here we have p1 and p2 those our propeller shaft first order and second order vibrations I’m going to add a vibration there’s a box here to add a vibration I’m going to add third order propeller shaft vibration also because this has a unique propeller shaft with the flexible rubber joint rather than the universal joint but it has three flexing zazz it rotates okay so let’s see if we can pick up of our vibration that I have created on this car so go ahead and put it in Drive you’ll have to turn off the traction control there’s a little button in front of the shifter did you find that is it off okay so go ahead and let go of the brake and oh let go the part part brake off also there we go okay so now good so now we’ve got take it up to like 30 miles an hour now now we’re doing this on the hoist obviously you’d want to do this on the you don’t want to do this on a hoist you want to go out on a road test to do this but he’s going to try to maintain approximately 30 miles an hour and we’ll take a look at what the bar graph is showing us notice our t1 line t1 graph over here is is going up a little bit if it won’t stay steady downshift the transmission into like second gear or third gear and try 30 if that doesn’t hold steady then go to 40 sometimes you’ve got to shift gears to get things working like get things working like they should as far as we don’t want the transmission up shifting and down shifting like crazy while you’re driving now notice right here on the screen we’ve got a t1 line at 29 milligram Milla jeez I told you anything higher than 10 is is got a problem and over here we’ve got a p1 at 16 okay take it up to like 50 miles an hour now so we’ve still got our tire at 16 we have our p1 that at 1213 notice everything else is pretty low so we can ignore those so if we go to frequency this shows us the amplitude level going up and down and the frequency goes across the x-axis here at the bottom of the screen and we’ve got the p1 amplitude which is how hard it’s shaking right here and the t1 okay go ahead and let off on the gas just let it come down to an idle but put the transmission in neutral okay step on the brake put it in park okay now will you hop out and let’s let’s move the sensor up to the the engine itself I want to show you what happens with the so come on out take the sensor with you you can maybe just stick it to the hoist and go around or find someplace on the engine itself that you can attach that magnet to okay so the screen goes crazy while he’s trying to attach the magnet just a bolt or something there we go perfect okay so now looking at the get the reflection out of the way here looking at the screen we’re picking up an e for vibration but that’s on the engines side of the motor mount and the the engine side of the motor mount is supposed to have the e for it’s a normal vibration if we go to the bar graph the ephors should be fairly high notice it’s right there bouncing off at 10:11 jumping around millage ease so that’s a normal vibration to have on the engine now can I get you to move the sensor just over to the fender the inner fender or the radiator support so that we’re off the engine now and let’s watch that go away and what you can do with the sensor is check your motor mounts to see if they’re working like they should to check your transmission mount your body mounts exhaust mounts there now he’s got it on the radiator support notice we’re clear down to four three two bounce around a little bit milah jeez sorry about the reflection there and it appears the engine mounts are doing what they are supposed to do so this is a fantastic vibration analyzer package we’re picking up the engine rpm off of the data link connector through the J 2534 interface we have a NVH sensor that we can move around with a very long set of chords that we can move just about anywhere on the vehicle and the frequency over here with the amplitude level I’ve got an e4 over here the e1 we’ve got a spike right here but notice that doesn’t have anything labeled with it and it could be and and most likely is a vibration that we ignore it might actually it looks like it’s double of the e4 it’s probably the e8 but sometimes all of those vibration analyzers and I haven’t investigated this one yet we’ll give you frequencies that don’t correspond to any rotating parts on the vehicle and in that case I would suggest that you just ignore them and go with what the number one vibration is that is identified as one of the rotating parts on the vehicle now there’s there’s advi– bration over here that I mentioned where we added the third or fourth order no what did we add we added a third order prop shaft let me put eight to order engine in there see it’s not a Thor Duran Genaro engine would be over here so it’s just something we’re gonna ignore and that’s fairly common whoops turn that off for vibration diagnosis okay well this has been a demonstration of the general motors Pico scope NVH kit and how to use use it to diagnose which group of rotating parts on the car we go ahead and turn the key or turn the engine off but then turn the key back on so thank you that’s that’s that’s all I need the the thing you do now which is the same as any other vibration analyzer is once you’ve got it narrowed down to first second third order tyre and if you recall order means how many shakes per revolution that device is creating so first order is one shake per revolution so t1 is for one shake per revolution of the tire t2 is two shakes per revolution of the tire t3 is three shakes per revolution of the tire we’ve got the e1 and the e4 we’ve got a those are engine first and fourth order vibrations we’ve got P 1 2 and 3 those are propeller shaft of vibrations first second and third-order and on this vehicle I put some extra washers on the propeller shaft bolt at the pinion flange to make it out of balance on one of the tires I put some extra adhesive weights to cause a vibration and on the hoist wear this is a limited slip differential both rear tires turn the same speed and so it worked ok on the hoist to do it this way but you guys need to remember that on a vehicle with an open differential or even the the Eton g80 Locker it will act as an open differential and those tires can turn at different speeds on the hoist and you should avoid using the hoist because it can give you some misleading numbers that you would never see on an actual Road test all right now the big question is is once you’ve narrowed down which group of rotating parts is the problem what do you do about it well you in this software you can bring the mouse over and click on p1 right here and p1 the little window pops up and it reads first order propeller shaft or prop shaft speed related vibrations can cause one shake or disturbance for revolution of the propshaft on standard four-wheel drive or all-wheel drive vehicles don’t forget that the front prop shaft can also cause this same type of vibration a shift vehicle in and out of four-wheel drive in an attempt to verify and isolate the concern obviously that doesn’t apply to this Camaro but click here for more information and when you click here for more information it brings up the vibrates software help file for first-order propshaft vibrations and it tells you what those vibrations are typically caused by and it’s caused by a component that’s out of round that’s rotating the same speed as the prop shaft or a component that is out of balance and so it has step-by-step procedures for you to diagnose this this refers you to the GM service information to measure propeller shaft run-out and then also to refer to the GM service information for checking imbalance and the this software provides tools to do a stroke balance on a propeller shaft okay so if it’s a t1 vibration like we had will click on t1 and it tells us first order tire speed related vibrations are caused by or caused one shake or disturbance for each revolution of the tire click here for more information up comes the vibrate software help file for first-order tire speed related vibrations and it gives you a number of things to check and in this version of the file help file you are to go back to the GM service information and follow the step-by-step procedures in the GM service information for measuring a tire that’s out around a tire that’s out of balance a brake drum or rotor that might be out of balance an axle flange or hub that’s out of round will stud circle run out stiff spots in the sidewall you might have a radial force or lateral force variation problem or even axle problems and so those are the things that you check that work that can cause this type of vibration so with this software once again and the NVH analyzer and the interface with a data link connector we can narrow down the group of rotating parts on the vehicle and then we can look at the help file of force step by step procedures of where to go and how to diagnose each individual thing and those are listed in most likely cause to least likely cause also so this is a I believe a very impressive tool as I said before it can work on non GM vehicles but you will need the non-gm software that you can download from pico scopes diagnostic website for free and then it’ll work on any vehicle all right well that wraps it up for this episode our next episode I will show you the generic version of this software and the generic kit for independent shops and how to use that have a good day


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