CHEVY CRUZE CHECK ENGINE LIGHT P2097 P0420 & P0324 DIAGNOSIS

[Music] hey guys what's up it's eric with advanced level automotive welcome back to the channel welcome back to another case study today we're looking at this 2014 chevrolet cruze it's got the four cylinder 1.4 liter engine this is a turbo now this car actually belongs to my little brother he's saying that the check engine light is on and it's got a little bit of a hesitation whenever you go to accelerate you guys already know how we do it let's go ahead and get started okay so we're in the vehicle the engine is actually running at the moment and if you take a look over here near the tachometer you'll see that we have the check engine light illuminated hopefully you guys can see that so i've got my scan tool here we're going to go ahead and click on trouble codes and as you guys can see we have three different codes stored in the ecm starting up here at the top we have a p0324 knock sensor module performance then down here we have a p0420 catalyst system low efficiency then down here we have a p2097 post catalyst fuel trim system high now i will say that my brother actually recently replaced the catalytic converter about two months ago so if you guys take a look we still have this p0420 and that code was the reason you replaced the catalytic converter so that is something we need to take into account this catalytic converter is pretty much brand new and we still have this po420 so there may be something more going on here now what i like to do whenever i run across a vehicle that has multiple codes like this is i like to think of things as a cause and effect is it possible that one of these codes is causing these other codes to get set that's really where my thought process is right now and particularly i want to focus on this p2097 this post catalyst fuel trim system hi because i believe what this is saying is that our downstream sensor is reading rich so let me take a quick moment to pull up the code description and we'll see what this code is all about okay so i found this website here that gives us a code description now i already went through this i don't want to bore you guys but essentially this code is pretty much what i thought it was going to be so again the code description p20 97 post catalyst field trim system too rich essentially what it's saying is that our downstream rear o2 sensor is reading rich and if we scroll down here you can see we got some symptoms you can see we have of course the check engine light is going to be illuminated poor engine performance decreased fuel economy and then it gives us here common causes for the p2097 uh we could potentially have a clogged or leaking exhaust or a problem with the o2 sensor or its circuits so pretty straightforward if we scroll down here they got a little picture of the oxygen sensor downstream again what this code is telling us is that this downstream sensor is reading a rich mixture even though the upstream is probably reading normal because at this point we don't have any other codes related to the fuel trims so i guess what we need to figure out is whether or not we actually have a rich condition or do we have a sensor that's just not reading properly okay so we're back inside the vehicle the next thing i want to do is i want to go ahead and pull up some live data and what we're going to do is we're going to take a look at the front oxygen sensor and compare it to the rear one so here we have our two data pits for the oxygen sensor and we have the heated o2 sensor one and two so we're going to go ahead and select both of these one and two then i think while we're at it we're going to go ahead and select the field trims we have the short term here and the long term field trim then we'll see if there's anything else here that we can take a look at we could probably go ahead and add the mass airflow sensor okay so we've narrowed down the screen to the data pins we want to focus on and if you guys take a look at the field trims over here you can see our long term is sitting somewhere around 14 so it is running a little bit lean at the moment our short term staying around zero here so um yeah we do have some lean condition happening here though it has not set a code for it but what i want to try to do next is i want to go ahead and raise the rpm up i'm going to hold it somewhere around 3000 rpm let me get up there and then we are going to hold it steady right around 3 000. we're going to take a look at the field trim numbers and we're going to see what happens here so if you guys look you can see we're counteracting here we have uh negative 11 negative 12 and so that's zeroing out so it definitely looks like we have some type of vacuum leak because when we have the rpms up at 3000 the field trim numbers do get better and then again i'm going to let off take a look at the idle wait for this thing to come down and you guys can see it idle we've got about 10 on the long term and well it's staying close to around zero here on the short term so yeah again just a little bit lean not really something i'm too concerned about but let's go ahead and take a look at the mass airflow sensor you guys can see we're at 1.8 grams per second which is normal again this is a four cylinder 1.4 liter engine so 1.8 grams per second sounds about right i want to go ahead and focus on these two data pits for the oxygen sensor so i'm going to go ahead and deselect the rest of them then i'm going to go ahead and merge them into a graph okay so if you take a look at the graph you'll see the blue line up here that's going to be our upstream o2 sensor and this green line down here that's our downstream uh now immediately what you'll notice is that our upstream oxygen sensor is switching like it's supposed to so you'll see it go from zero to one volt switching like it's supposed to but if you take a look at bank two which is the green line here it's pretty much just flat line now one other thing i wanted to add is that this vehicle still uses a conventional style cubic zircona o2 sensor for the upstream this does not use an air fuel ratio sensor which if you ask me seems a little bit odd because this is a 2014 vehicle you would think that by this time they would have switched it over to an airfield ratio sensor but it's still using the old-school switching type no big deal plus it makes it a little bit easier for us to diagnose i kind of like the system better so again focusing on this flat line down here uh what i want to do is i want to verify whether or not this oxygen sensor is even responding at all now there's actually a couple different ways we can do this you know we could inject propane into the intake to see if we get a response from this downstream sensor but one really quick thing that you can do without having to get out of the vehicle is actually just to blip the throttle so what i'm going to do is i'm going to use my foot to just floor the accelerator for a moment and let off and what that's going to do is that's going to induce a quick lean condition in which the sensor is going to respond and then it's going to have a rich condition and we should see that movement on this bottom sensor here so i'm gonna go ahead and blip the throttle body you guys hear that and you can see right there our voltage went up all the way up to close to about one volt it went down went back up again went down and now it's just pretty much flat lined again let me go ahead and flip it again there we go again you can see where i hit the accelerator it went down it came back up and again it looks like it's just flat lining so to me it does look like this oxygen sensor is responding i guess we could see what happens whenever we hold it at a higher rpm so i'm going to go ahead and get up to let's say 2500 rpm right around there i'm going to hold it steady and let's take a look at the graph here again you guys can see the initial throttle there but it's pretty much this flat line you can see the frequency increase on that upstream sensor but we're pretty much just flat lined here now the other odd thing about this is that our code is saying that our downstream sensor is reading rich but if you look at this um you know we're flat lined down at the bottom close to zero volts that's an indication that it's reading lean not rich so i'm wondering why it would set a code for this downstream sensor to be reading rich when in fact we're looking at it right now and the voltage is low rather than the voltage being high no big deal i'm not going to worry too much about it you know sometimes we just don't have an explanation for why one code gets set versus it setting a different code but right now i think what i'm going to focus on is trying to figure out why we're showing a lean condition on this downstream sensor again one of our possibilities is that we could have an exhaust leak and to be honest with you guys i think that was one of the first things that i noticed when i started up the vehicle is that it does sound like it has an exhaust leak let me take you guys outside and let you listen okay so moving under the hood i don't know if you guys are going to notice it on the camera especially because right now my neighbor is actually mowing his lawn but if you guys listen really closely you can hear what sounds like an exhaust leak hopefully the microphone is picking that up and again like i said my brother actually just recently replaced the catalytic converter so that is one of my concerns there is whether or not we might have an exhaust leak here so i think the next thing i want to try to do is i want to smoke test the exhaust and see if we can find an exhaust leak okay guys so let me show you what i'm working with so i got my smoke machine right over here you can see it's connected to the compressed air and right over here i have my battery pack that i'm using to power up the smoke machine and right over here we have the hose now i do have an adapter that goes into the tailpipe right here but i actually misplaced it so what i'm gonna use is just a funnel so we're gonna go ahead and stick that into the exhaust pipe i'm gonna go ahead and slide this in there make sure we have a nice tight seal then i'm gonna go ahead and push this button on the top of the smoke machine you'll see it turns red and we should have smoke coming out of this in just a second once it heats up there we go we got smoke coming out so i'm gonna go ahead and shove it into the funnel here now we're gonna let the exhaust system fill up with smoke and see if we can find a leak okay so first of all let me apologize for the bad camera angle i had to crawl up underneath the vehicle there was not a whole lot of space but as you guys can see i was able to locate where the leak was coming from what we're looking at here is where the catalytic converter meets the down pipe and you can see that we have a leak where this three bolt flange is so obviously the first thing we need to try to do is replace this gasket and see if that fixes our leak okay guys so i went ahead and i installed the new gasket as you can see i got everything bolted back together this is the old gasket right here and you can see that it's got this kind of blacked out area right here looks to me like that's probably where the exhaust leak was happening now i will say that these bolts were pretty loose i don't think that my brother really tightened him down like he was supposed to and plus he put the locking washers on the wrong side but you know i'm not blaming him i went ahead and i tightened it down so let's go ahead and move back inside the vehicle and check out the scan tool okay guys so we're back inside the vehicle the engine is running and it's idling and take a look at this graph here you can see that both sensors are now working you can see our downstream sensor is switching properly again our downstream was this green line you guys remember before we replaced that gasket this was pretty much flat line down here at the bottom you can see all this activity now we have you can see it's slowing down here once the engine's warmed up you can see that both of the sensors are switching like they're supposed to but if any of you guys know what the downstream sensor should look like and why i'm worried about what the signal looks like right now because again you guys remember we have a po420 code which was a catalytic converter and of course the way the computer sets that code is that it's comparing the upstream and the downstream sensor because there should be a delay that's happening between the switching of the upstream sensor to the downstream sensor now if you guys look i mean we're almost pretty much exactly the same so when the blue line is going up you'll see the green line going up we have these humps that are pretty much almost matching they're just too close in time really what we want to see is much more of a delay on this green line so we should have some switching you know for every two to three humps of the blue line here you should see one hump of this green line hopefully you guys understand what i'm trying to explain but essentially when the downstream sensor is switching at the same rate that the upstream sensor is you know that's an indication that the catalytic converter just is not doing what it's supposed to be doing in other words it's not converting the gases like it should it's not storing the oxygen like it should so you can think of it pretty much like the air that's coming in is the same air that's coming out and that's exactly what we're showing on the graph the same air that's coming in on this blue line here is the same air that's coming out on this green line here so we fixed a problem we fixed that p2097 because now we have switching going on with this downstream sensor but i'm still worried that we're going to have a problem with this po420 now the po420 code for a lot of you guys who don't know of course it means the catalyst efficiency below threshold means exactly what it says the catalytic converter is not doing what it's supposed to be doing it's not converting the gases and it is one of the very few codes that i like to say is one of those codes that it is what it is i mean the computer is looking at the front o2 sensor it's looking at the rear one it's comparing the two and if it sees that they pretty much are sharing the same frequency it's going to set that code so at this point i'm pretty sure that he's going to need to replace the catalytic converter again hopefully he can get this thing warrantied out but i think what i'm going to do right now since we solved this problem with the p2097 is we're going to clear the codes and we're going to drive it and we're going to see if that po420 comes back my guess is that it does there's a high probability of it but there is a chance that maybe us fixing that exhaust leak may have done something to maybe improve the signal hopefully the computer sees this and is okay with it but i mean at this point i just don't know i wish i had more of a solid answer for you guys but again the po420 code it is what it is looking back at the scan tool real quick i wanted to address something and that is the field trim so if you guys take a look here at the long term in the short term uh you can see we're kind of more in a normal range than we were before so if you guys remember before you know we were looking at like 15 on the high end um and if you look now we're at eight on the long term and we're kind of showing a negative here kind of jumping back and forth but it seems that the field trims have gotten better during idle now i don't know if that has anything to do with us fixing the exhaust leak it is possible i mean generally people will tell you and textbooks will tell you that the downstream o2 sensor does not affect the field trim values but i will tell you i have seen it on some particular vehicles specifically a nissan that i had where the downstream sensor was directly affecting the field trim values so i wouldn't be surprised if because our downstream sensor was reading lean all the time it was directly affecting or indirectly affecting the filtering values okay guys so while we're at it one of the things i'm going to do real quick is i'm going to go into special functions here and i'm going to go into reset functions we're going to reset the field trim value and what that's going to do is it's going to allow this thing to relearn the field trims and get them back to where they need to be so i'm going to go ahead and hit reset and now it's zeroed out so we can go ahead and back out one other thing that i'm gonna do while i'm here is a quick camera crank relearn or this crankshaft position variation learn i'm gonna go ahead and click on this now this is something that's oftentimes overlooked but i found that a lot of times this can solve uh some drivability problems that you might have and if you guys recall we do have a code uh po324 for the knock sensor now i really hadn't looked into this yet but you know as far as simple things we can do just to be preventative and also make sure that this thing is running in top shape this is right there at the top this is something quick and easy that we can do so again i'm going to go ahead and hit ok here now it wants us to accelerate [Music] learning progress test passed successfully so we have now done the cam and crank relearn so we can go ahead and go back to the live data because what i want to do is i want to take a look at the data pids for the knock sensors so i'm going to come over here for the ignition click on this if you look right over here we have the knock we're going to go ahead and select that there's also a total noc we'll do that and the nice thing about this one is that it actually gives us individual cylinders even though there's only one knock sensor it does give us individual cylinders on the data pits here so we have cylinders one through four and i guess we can go ahead and throw in the engine timing while we're at it so i'm going to go ahead and narrow the data pits down to this you guys can see everything right now looks pretty normal the engine is idling we have no here that's showing us that we're not detecting any knock throughout the cylinders we don't have any knock what i'm going to do is i'm going to go ahead and raise the rpm up and kind of go through the rpm band now i might actually be normal to see a little bit of movement here but you know what we don't want to see is something that's happening excessive i think what the computer is looking at is it's looking to see if there's any knock that's happening for a certain amount of time so let's say if the threshold is like 10 seconds you know it wants to see that there's knock occurring for at least that certain amount of time before it actually sets a code again i'm just kind of raising the rpm here i think i'm somewhere around 2800 i'm going to get up to 3 000. you guys can see we don't have any activity we get up to uh around 4 000. kind of see a little bit of activity there right now i'm at uh around 3200 so i don't see anything excessive i'm going to go ahead and let off of course during the decel you might see some but we don't show anything excessive now what i want to try to do at this point is i'm going to go ahead and clear the codes and take this thing for a pretty extensive test drive and i want to see if this code actually comes back because again you know we're not really sure if we fixed it you know it's possible that after fixing the issues with the fuel trims um with the exhaust leak and whatnot you know we may have affected this so it is possible that we may have fixed the problem i'm not really sure but there's really only one way to find out but before i go on a test drive i do want to take you guys under the hood to show you something that i think might be worth taking a look at okay guys so moving back under the hood um what i wanted to show you guys is that if you listen closely i don't know if you guys are picking it up on the camera here but if you look at this tensioner down there you see that spring that's jumping up and down yeah that thing is rattling a lot so if you look at the top of it you can see that whatever that is on that spring tensioner has come loose and so i will say that you know i am kind of concerned that this tensioner might be resonating some noise through the engine because right now i don't hear any knocking while the engine is idling or while it's running but i do hear this rattling so i am concerned that the tensioner might need to be replaced and maybe that there's a small possibility that it could be setting off our knock sensor because again like i said if it's loud enough it's going to resonate through the engine block the knock sensor is going to pick that up it's going to detect it as knock it's going to set the check engine light maybe the engine timing cause performance issues so you know i think at this point that's just something i'm going to keep in the back of my mind i mean this obviously needs to be replaced anyway you can see how it's just jangling around there so you know that's going to be next up on the list but i'm going to go ahead and take this thing for a test drive and see if our codes pop back up all right guys so i've been driving for about 30 miles now as you guys can see the check engine light just came on sorry it's dark outside now but yeah the check engine light is on let me take you guys over to the scan tool and show you guys what i was watching okay so you guys can see the data pins that i was watching while i was driving essentially what i was watching were the knock sensor data pids looking to see if there was any excessive activity and i'll tell you right now it actually looked pretty good while i was driving so let me show you guys right now we're at the standstill i'm going to go ahead and start accelerating and we're going to get up to cruising speed and just watch those data pits i mean you'll see a little bit of activity but nothing excessive so the vehicle is moving at the moment we're up to 25 miles an hour let me get up to 35 40 miles an hour at the moment and we're cruising at about 40 miles an hour right now i'm coming up to a stop light so i'm gonna slow down okay so judging by the data pids and what i saw i really doubt that this check engine light is going to be for the knock sensors because again we didn't see any excessive movement or excessive activity from the knock sensors we saw a little bit but that's probably normal what i'm thinking is that it's more than likely the check engine light came on because of the catalytic converter if you guys recall we had a po420 before and i was worried that that code was going to come back because of the activity that we saw from the downstream o2 sensor so let me take you guys over to the scan tool and let's see what code we have okay so here we are at the scan tool once again i'm going to go into the trouble codes and let's see what we got bam po420 what did i tell you guys i was pretty sure that this code was going to come back because again that downstream o2 sensor was showing a lot of activity and it was pretty much mirroring or showing the exact same thing that the upstream sensor was showing so at this point i don't think there's any way around it it's going to need a replacement catalytic converter anyways guys i'm going to end up the video here i'm just hoping you guys were able to pick up some useful information maybe to help you guys diagnose something maybe if you're working on the same vehicle running into the same problem now i wasn't able to give you guys uh complete answers to certain things of course i'm gonna keep you guys updated on what goes on with this vehicle we'll see if our engine knock code comes back also the catalytic converter we're gonna go ahead and replace it and i'm gonna give you guys a before and after so look forward to seeing a video about that anyways like i always say thank you guys for watching i hope you found it useful i hope you find it informational if you did make sure to give it a thumbs up if you haven't done so already make sure you subscribe to the channel hit that notification bell and i'll see you guys in the next one thanks [Music] [Music]

Channel: ADVANCED LEVEL AUTO

Views: 11,829

Rating: 5 out of 5

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Id: s1CT3ZW2_4M

Length: 22min 5sec (1325 seconds)

Published: Fri Jan 15 2021