Air/Fuel Sensors (Wideband Oxygen Sensors) vs O2 Sensors- PART 2

is to use a snap throttle test and what that means is taking the the throttle and wide open throttle all the way for just a second and then let it go and that is going to give a very characteristic pattern that they're showing here that indicates that the air fuel sensor is working because doing that snap throttle is going to test the sensor in both directions lean and rich so what that's going to look like is you of course will be at your perfect stoichiometry and then when you snap the throttle here and you go to wide open throttle you're going to see a sharp decrease in the voltage and then almost immediately when you let go you're going to of course create an extremely lean condition so you're going to get an increase in voltage and then it's fairly quickly going to stable back out so this is the pattern that you could use without even getting your fingers dirty or anything we are of course going to do all of these tests with the propane the intake leak and the snap throttle I can tell you that I have done this test on a toyota before and it looked exactly like this absolutely exactly like this so if you have a Toyota that's great I can tell you I also did this on a Ford that used a wideband sensor and it kind of really didn't look very much like that and I'm not really sure what's going to happen on the Subaru but one thing I do know that's going to be different as these voltage numbers will be different that's that's almost guaranteed but this pattern may not look exactly the same so I'm going to do all the methods and we'll just see what happens and while I'm cleaning up you guys should point out that again because of the extreme temperature that Oh to send that wideband sensors work at they typically like late-model cars with o2 sensors there are heater circuits so the other thing that often goes wrong with a sensor isn't so much the sensing but the heater circuit can give different trouble codes different check engine lights so those are identical just like with a regular oxygen sensor you would look for continuity on the heater circuit in the sensor itself and you would do the same thing with a wideband sensor so things really don't change the other thing that doesn't change is your understanding of fuel trim fuel trim whether it's derived from oxygen sensor data or wideband o2 sensor data fuel trims don't change thank goodness another there was something we don't have to adapt to but if you understand fuel trims and you use them in diagnoses like you should then that doesn't change just the source of the information changes a little so let's talk about one other thing that can be very useful in your diagnosis of a wideband oxygen sensor to determine if it's faulty or not hey so when you look at your air fuel sensor on a scan tool and you pull up your pins for it and it could say wideband oxygen sensor it'll probably say something like Bank 1 s1 wideband o2 something like that or Bank 1 s1 AF something or other some some scam tools even say lambda sensor whatever but whatever the case is you're going to have several different kids and one of them is going to be sort of all what the hell is that pit obviously one of the first pits you're going to generally use is the voltage you also may be able to have a milliamp pid' and some scan tools may not even be able to really read that or even show that as an option but you're also going to get another kid showing up on your scan tool that actually I find to be pretty useful and that's going to be your equivalence ratio kid what in the hell is that so what the equivalence ratio is is it's a really great diagnostic tool that you can use because as we've seen many different cars can use many different standards for their voltage outputs so let's say you have Toyota here and we know that's going to be 3.3 volts the Subaru was somewhere around like 2.25 or 2.5 volts something like that Ford was somewhere around I no but we'll just say three volts okay the thing is these are all normal stoichiometric readings for those particular cars and maybe even that in that particular model year as a matter of fact well the problem is you don't know that so unless you can find what that information would be you can easily see where if you've worked on Toyotas your whole life and you get used to this as being stoichiometric and then you work on a Subaru and you see that this Subaru is stuck at 2.5 volts you might be inclined to say oh this is the reason why there is a rich code in this car because this wideband o2 sensor is stuck rich well no it's not it set stoichiometry it just uses a different voltage that's all all three of these are in stoichiometric but what an equivalence ratio does is the equivalence ratio we'll just call it an ER sets stoichiometric at one regardless of the voltage system so this kind of normalizes for you regardless of the system you're looking at to be able to determine if the car is indeed at stoichiometry at this voltage so if you look at say this Ford which is at 3 volts and you're not sure if this flat line at 3 volts is stoichiometric you can pull up the equivalence ratio on your scan tool and if that equivalence ratio is 1 then you know that this is the normal voltage reading imaginary reading for that Ford and if your variance from the equivalence ratio is greater than 1 then that is going to indicate a lean condition and if your equivalence ratio is less than 1 that is going to indicate a rich condition so you can get by using the equivalence ratio with or even without the voltage and be able to determine if you're getting responses leaner rich with the car so I think what we're going to do now is go ahead and take all of this information because all of this information is assuming that I'm understanding it correctly and we are going to test it by going ahead to warm up the Subaru and see how this stuff actually looks when we apply it real-time on to a car so let's go see what happens okay I'm going to go ahead and set up my scan tool while the engine warms up and during this time I want to point out just for the record that I hate Subarus I hate them I hate their 180 degrees cylinder heads I hate them but it's the only car that I have available right now that I know has air fuel sensors so let me go ahead and get this set up and then we'll see how close the data and information that we went over actually applies in a real scenario alright and I know people are going to be asking what is the scam tool I'm using this is going to be Auto ingenuity I talked a little bit about this in one of my other videos where I compared a couple of scam tools that I like to use both of them PC based so if you're interested in buying a scan tool especially after this video then you can click on my name shorteners box and it will bring up my pit channel and then from the channel you can find my video for the scam tools but also maybe I'll put it in the description below but let's go ahead and pull up our wideband oxygen sensor voltage right there it is so again this is a four cylinder so which the fact that I Drive a four cylinder car is embarrassing enough much less a Subaru to be honest but as with oxygen sensors you would have one wideband o2 per Bank same thing as an oxygen sensor but we're going to go ahead and do the voltage now when I do that we can see our voltage scale here and we see that we're actually at two and a quarter volts almost we see the actual numerical number given there so this is actually lower than what you would get with my examples that I gave with the Toyota but as I said this voltage is going to be different for different cars different years different makes different models the question is is this a good number well I don't know so that's one of the things we're going to want to do is find out maybe it should be 3.3 volts like a Toyota and this number is not actually at stoichiometry well what's a good way to know let's do this let's go ahead and look at that equivalence ratio because if this engine is in stoichiometric xual voltage for stoichiometry on this particular car that equivalence ratio that I mentioned before should be one so let's go ahead and pull out the courtland's ratio and there it is right there the wideband equivalence ratio and there it is and we can see here on our scale for equivalence ratio that we are indeed at one so good indication that we are either running at stoichiometry or The Oath the wideband o2 sensor is stuck in stoichiometry which is unlikely this is really a fairly new car but we can see that as I have stated this is according to plan so let's let me do a couple of adjustments here one of the most important things you want to remember is that with your sensor on a wideband you're going to get less of a amplitude of reaction than you will with an oxygen sensor so I just want to quickly adjust a couple of the scales here so that I can maximize any difference that we expect to see okay so I've sort of adjusted the scale to amplify anything because I expect there to be fairly minimal changes here remember these voltages are not real and we'll look at that in a little bit the first test that I want to do is let's go ahead and do that test that we saw with the Toyota sensor that I described worried if I do a wide-open throttle we should get an immediate dip and then an immediate rise and then a stable and remember we should actually see that on both of these traces I believe but really what we're looking at is the voltage of the red trace so I'll have to get into the car to do this so let's try it oh well I'll be darned look at that it actually did seem to reproduce that trace I I haven't seen that all cars tend to do that and then it stabilized out again let's try that one more time all right I'll be darned now it doesn't look nearly to me like the trace shown for the Toyota let me go ahead and bring that up real quick just to show you okay so this is the Toyota document from the engineers at Toyota and what I'm looking at is the amplitude for the rich condition and lean conditions seem to be equivalent here in other words there is just as much of a dip as there is a rise here and then it levels out however we don't seem to see that on this car there is definitely a dip and arise but watch the amplitudes they're different I think so we can see the dip is not nearly as much as the rise compared to the Toyota but it's still fairly similar so I'm pretty satisfied the bottom line is this is clearly a functioning air fuel sensor so if you had a lean code or a rich code that says something bla bla bla bla bla air fuel sensor blah blah like most people would interpret you would know based on that test almost certainly not to replace the air fuel sensor so let's go ahead and try a couple other things one of the things that I want to do let's go ahead and pull a vacuum hose and see what the response from the computer is now before I do this remember what is the reaction that we are expecting to see remember it's going to be backwards on an o2 sensor we would expect to see these numbers go lean by showing lower voltage but if my understanding is correct on this what we're going to expect to see when I make this lean condition by pulling the hose we're going to see the voltage and so the equivalents increase okay so let's see if that actually happens maybe you can hear the vacuum leak almost killed the engine there but unquestionably it did increase so that test works pretty good let me go grab a can of propane and let's see if we can do the opposite all right I'm going to add some propane just directly into the airbox here just briefly and let's see if we get and you see it does indeed go rich which does look a little bit backwards and of course the fuel trim is correcting because I'm really not adding that much into here yet let's add a little more and we see it does indeed have the predicted response so that's all really cool that actually turned out to be quite satisfying there is one other thing that I want to do though and this is really a lot more for my personal interest one of my favorite tests that I like to do is to look at a wide open throttle test while driving it's one of the few times that I actual actually literally use the oxygen sensor data in a diagnosis normally again like I say you're like a detective and the oxygen or wideband sensor is your witness so it's reporting a situation and your first thing is is my witness lying or are they telling the truth and once you determine the witness is lying well then you're done you need a new witness you need a new oxygen sensor air fuel sensor because your witness is faulty however if the if you find that your witness is reliable well then you don't sit there and investigate the witness you look at the things the witnesses telling you and you follow those things to get your diagnosis so you really don't so much use the witness itself for your diagnosis you don't really look at a o2 sensor trace and use that as a diagnosis you just look at this trace to help determine that it's functioning however there is an exception that I use on that and that is when I am diagnosing a lean condition and I want to see if the condition is related to the mass airflow sensor or the fuel pump in other words a lean condition that is because of a dirty math or poor delivery from the fuel pump and what that pattern is going to look like is again you're going to be because of your fuel trim in stoichiometry but then when you floor the pedal which on this Subaru is going to be less than satisfying because I don't know how people with four cylinders do this but I don't expect it's going to go very fast but it is going to do something Universal I hope and that is it's going to go rich at wide open throttle and I know this from racing my Trans Am at the racetrack while connected to my scam tool I can tell you that when you floor a car it's going to go rich at wide open throttle and this is actually a hugely important diagnosis because if you for that pedal and at wide open throttle you see your o2 sensor go lean this is the only time that I really use the actual data from the o2 and a diagnosis I am going to call at wide open throttle if I see that a bad mass airflow sensor or a bad fuel pump some type of delivery problem of the fuel is an issue and that is something that I do not want to lose the capability of doing because of an air fuel sensor so what would we expect let's let's do this on the Subaru soon we know now that our stoichiometry is at about two point two volts now and let's put 3.5 up here and let's put 1.5 here so if we're at stoichiometry in our Subaru and I floor it what would the expected response be well it's going to be that it should go rich which means that we should see a decline in voltage and again that's that funky interpreted voltage but I really want to see that because this is one of the most important diagnoses that I typically do in diagnosing lean conditions and I have other videos that show this I don't want to lose that capability on an air-fuel sensor because it's very important so what I want to do is go drive the car floor it and see if I get this response now I'm not going to bring you along with me you have to wait in classroom because of safety and I don't want to film this and everything but I'm going to do a screen capture and we'll see what happens when I floor the car all right I am back from my uneventful test drive although I do have some good data here but I just wanted to say as much as I hate that Subaru it reminds me of how much more I hate 4-cylinder engines for the life of me I do not understand how they calculate the zero to sixty time on a four-cylinder engine because by the time that car gets up to 60 I'm already where I need to be let me orient you here we can actually ignore the red and green lines I was just doing some fuel trim experiments there to show that fuel trim is the same thing whether you have a wide band or a narrow band oxygen sensor so ignore those but what we're looking at here is the blue line and the blue line is the sensor voltage for the wideband sensor and we can see the scale is actually shown over here so we can see that we're at our two point two volts at idle and we're still at idle and then right here I floor the car and I kind of in retrospect now wish that I had adjusted the scale like I did earlier to be able to detect this a little better but there is indeed a rich condition here that is shown by the air fuel sensor at wide open throttle which is as we would expect although it's not nearly as prominent as what I would expect and we can also see that actually it increases ever so slowly in richness as I continue to hold down on the throttle and luckily in a four-cylinder car you can hold the throttle down for a very long time because it doesn't go faster when you do it but it sure sounds like it does and then here I go ahead and I just let go of the throttle which of course greatly creates a lean condition which is very prominently reported by the sensor and then it pretty quickly levels out again but while I'm happy to see that I can detect the rich condition at wide open throttle here it's not very prominent and again I don't know whether this is simply because that's the way it's reported on this car Subarus are very well known for their fuel efficiency especially these later models maybe this is just some type of fuel efficiency kind of thing that's going on here but the bottom line is that I'm very happy to see that I can detect a rich signal from the air fuel sensor at wide open throttle the point of it is had I been diagnosing a lean condition and I had seen the opposite where I get a little bit of a lean condition at wide open throttle it does give me direction on where to go to help solve that lean condition so this is very satisfying all right well that's it for my training at this point I've achieved my objectives I feel like I do have a very good understanding of the air fuel sensors because I was able to validate what I understand and predict what would happen given various conditions on an actual car I feel like I'm pretty confident I would be able to diagnose a faulty air fuel sensor and I also feel like I can use air fuel sensors to assist me in my diagnosis so today was a really good day and I really hope that it was for you too and that you learned something so thanks for joining me in class today we'll certainly do it again sometime and I wanted to say real quick thanks to you guys while it's not a very big thing I did actually reach 1,000 subscribers on my last video last month so I really appreciate it and I do appreciate you guys taking the time to watch my videos and all the feedback that I get even the negative so I appreciate it very much I hope you found this helpful we'll see you next time

Channel: Schrodingers Box

Views: 112,317

Rating: 4.9324088 out of 5

Keywords: fuel trim, LTFT, Long term fuel trim, short term fuel trim, stft, scannerdanner, eric the car guy, oxygen sensor, wideband 02 sensor, 02 sensor, air-fuel sensor, P0171, P0172, P0173, P0174, Bank one lean, bank 1 lean, bank 2 lean, bank two lean, scan tool, engine problems, car stalls, engine runs rough, rough idle, vacuum leak, leaking injector, fuel pump, diagnose fuel pump, replace oxygen sensor, bad fuel economy, fuel economy, toyota sensor, yt:stretch=16:9

Id: K8GLH6ubXoc

Length: 22min 42sec (1362 seconds)

Published: Thu Mar 20 2014