How To Diagnose GM Knock Sensors - P0327 & P0332

their viewers and welcome back to the self made out of channel I got a cold uh anyhow I've got this Oh three shibby it's got the big 4.8 in it I think that uh mouth it has a code for some fuel system lien problems and they've already shot the parts cannon at it but nobody James you feel pump it's got about twenty pounds of fuel pressure circuits good all that yeah we're not looking at that it also has a knock sensor code in it the guys gonna take care of his old fuel pump I guess about wanted me to check out it take care of the knock sensor issue kind of a kind of a problem on these I do believe there's a service Bolton on it I don't know if we went back to this year and now but these have a little problem with the water getting under the intake and right the connectors off and you're supposed to build this silicone dam to keep the water out on the southern business alright I wanted to show you some quick easy ways to check knock sensor of course we use a lab scope here it's about the easiest way to check knock sensors and be honest with you you can check them using a regular you know digital voltmeter on the AC scale it's you know I've seen it before where it's not 100% definitive so you got to be careful with it but we're just gonna take a scope we're gonna look at these knocks and so I'm gonna show you what they look like sure test them and swap out the new ones because I do have one bad one on this but I can show you kind of you know bad versus good and we'll take it from there I'm not gonna show the process I don't feel good today and frankly I just don't have the time but I do want to show you you know what's up so here's the code we get it we get that po3 27 I think the other codes like a 325 because there's two sensors don't hold me to that fortunately GM has made it easy to work on so they put our sensor connector jumper harness right up here on the intake manifold so that's helpful so I do already have our scope hooked up and I'll show you how to test these so I actually code 327 and 332 or mb or low voltage code so what it does basically so you're knock sensors they're gonna create their own electricity there I guess what they consider a pzo crystal sensor kind of like you know some DPF centers and stuff like that so it's going to create its own electricity with with movement yeah I'm not an expert on that so you'd have to kind of look that up to learn a little bit more they do have a resistance spec on them some 1:1 test you can do on a knock sensor is a resistance check now we'll see let's see that's a switch my leads around here but we can do an ohm check on them now these are supposed to be around a hundred thousand ohms I think between eighty and a hundred thousand or eighty and a hundred and ten thousand or something like that so swap leads around here let's see so one of them is at a hundred and three thousand let me swap it with the other one we're hooked right directly just to the sensor and then to ground just a single wire sensor and the other one is 104 thousand so resistance wise they seem to check out okay so that proves it right there you cannot just base us off resistance alone because I know I have a bad one there's no question about that so that's one check you can do on them what the vehicle so that's a coinciding criteria for this is it looks for a certain amount of noise to be on that signal when the vehicle started at a certain rpm if it doesn't see it then you know we flagged this code that's kind of kind of it in a nutshell so right now we're we're hooked off we're AC coupled of course being a snap-on scope you got to turn to peak detector you're gonna get false positives I've got a trigger set now I got our green trace is actually on what they would consider knock sensor to and our yellow trace is on what they consider knock sensor one and knock sensor one is the one that we're supposed to have an issue with I got out I got a 10 volt scale we got you know we got 200 you know 20 milliseconds for division 200 milliseconds across our screen don't mind the sniffles folks so what we'll do in theory take it and if the engine detects noise or knock it's going to display an AC sine wave here and the amplitude and frequency will change when the intensity of the knot so we're gonna do is use the old pry bar and the old hammer and I'm gonna give her a little tap on the exhaust manifold and we should see a signal being generated you don't have to have the key on or anything for this we get down here on the manifold we're gonna give her a little path so we see that signal number two it's working and the harder you hit you know the higher the amplitude of the signal goes we don't hit too hard you don't wanna break the old girl I'm gonna hit towards the back in the engine and the rear manifold I can see we got a pretty good signal they're being produced the way that little finer detail here will change our time basis fifty milliseconds across the screen here should see that a little finer detail now but we can see our other knock signal down here or not sensor one is not working we know a couple things though we know it's hooked up we know it has good resistance it's just kaput you can look at this in a on a DV om of course it's just gonna average the voltage so it may be very low voltage you know like a tenth of a mole or something see 80 volts ought to switch our leads around here because our bleep number one is the one that doesn't work so we'll go on the one that does work so it's going to be sensor number two remember a little tap we'll see what the voltage is back on the dead one here this is for curiosity's sake to see what it kind of voltage it does produce if any a little bit there but if you're comparing them to each other it's clearly obvious that that one is spanked and you know I hope we're all getting something out of this hate work when I'm sick the other thing we can do too we can start it up see what kind of noise is on the known good one versus the crap you want we'll probably have to go on a lower voltage scale to get any kind of details well we'll drive her down to two volts here see what she says and keep bear in mind to that some actually have some oxygen systems I don't know what I'm working on here some knock sensors the signals will work on a bias voltage so let's say we had this plugged in or back probe in it wouldn't be uncommon to see it like you know in a two and a half fold bias and then you know pull down when it's plugged in and you will use that for circuit checks which you know isn't the case on this one there is no bias voltage on this it's like 150 millivolts or something floating on that line but anyhow let me start it up kind of see what we have here there we can see the difference now the ECM looks for a certain amount of noise you know I don't know what it's looking for as far as how much but it has a sub parameter that it looks more and when it doesn't see anything you know we get our low voltage Gordon if you're working on these old ship relays make sure you get the wiring harness for them they do have these little rubber plugs that go down in the course you got your single wire connector here's what the knock sensors look like this one's from Serbia these are from Mexico I tell you know it's genuine Chevrolet they have papaya baseball mercury there folks everybody driving domestics they think I hate Chevrolet well sir I'm making in the USA baby like Honda right yeah so there's an accent says they're pretty sensitive to torque specs and seal it and debris so lots of bulletins on them make sure you don't over tighten them and all that blah but we got to pull the intake manifold like I said I'd love to show that but my kind of a time crunch going to do a little camping this weekend so I got to get out of here on time today so I'm told by the boss lady so I'll get them in will recheck the specs once you get it together and take her from there you go fellas and take it off there was a sludge pit as I cleaned it up you know use the vacuum cleaner and my super scraper at any rate the front hall sensor numero uno was a rusty turd and you can see that it was drowned in water at some point it was clean this time the course was about I happened to rust sitting on the bottom of the hole but that's that knock sensor that's a knock sensor connector this is why you typically have to replace them now this was the rear one and you can see the difference so yeah it's all cleaned out new ones are installed torque to factory spec of course and the new harness put on now sometimes I'll take it out the front of b-tat silicone around these rubber plugs they quite nicely Jim did a good job on those so they do fit pretty snug silicone Amman follow the service Bolton you know whatever trucks 14 years old it made it this far in life so I figured and they got another 14 years left in it or four from that matter so up to you moments later it is back together we reattach our ground go back on this little guy here hooked our jumper harness what they can get plugged into it maybe maybe again come on little guy we got a wonderful funder I'm doing here yeah good enough let's see uh summertime cold suck just FYI I haven't had a cold in probably five years here we are see the banshee all right we're back giving the old tap guess we're gonna beat it on this side technically they should both work I hope wall we wrap change our voltage scale fella well we're done or add two volts for all cuz we're looking at it runnin big dummy all right now let's have a look so the amplitude of one of them should be a smidge while worried just because you know we're beating on the front of the engine versus the back by Barry but attached don't give her some very mild taps there's yes after give it a honk pokey what we can do terrific concept we'll go back turn digital multimeter volts ac to volt scale let's see if this is any different with the new ones not a whole lot different there folks of course that's just averaging the voltage well we can go back go back in our scope here we'll go ahead and put on our two bolts Cal we'll start it up and we'll see what kind of noise they have just add an idle you'd be willing to start necessarily no it's yes sir all right miss Hannah's gonna start it I am you're a couple okay that's that so they look like that an idol when they work alright shut off areally so - the glare I guess that's about it good of a job as we can do we're done we verify the repair we also verified it before we've repaired it this is what you have to do of course on these I've never seen it anything other than just an ox that's here so if you're in the market to take wild guess you'll probably get it right but you guys know we don't guess we test that way there I don't get burned the guy comes back swing it wait like a tiger there and folks that is some basic drop the lead sensor testing on your Jimmy now they're all pretty much the same no Shep you does use two different style knock sensors on these but I think that more has to do with how the ECM interprets the data now that's a pretty much free pretty easy pretty simple testing don't tighten the dog snot out of them you know it's supposed to be 15 foot pounds or so I'm just use your noodle don't crush them down and same thing with the intake and stuff you know torque to spec whatnot so moving it takes more alka-seltzer Colden side this stuff so I can breathe in breathe out the nose got the sniffles so anyhow that's it I'm gonna keep on a truck and got a bazillion things to do no time to do it this hands gonna take care of our tools and what she's doing that why don't you guys click that subscribe button if you haven't stick that way thanks and you know consider subscribing if you have if you want to stay updated every week and plants not patreon or socials and all that business and just little viewers if I can do it you can do it thanks for watching [Music]

Channel: South Main Auto Repair LLC

Views: 113,117

Rating: 4.9151306 out of 5

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Id: 1m-hftSBNwk

Length: 16min 5sec (965 seconds)

Published: Sat Aug 05 2017