Air/Fuel Wideband vs Oxygen Sensors (O2 sensors)- The Demise of Shadetree Mechanics? Part1

H hey what are you up to I am actually in class right now but I'm the only person in class so if uh you are interested in doing what I'm doing which is teaching myself about the new air fuel sensors also known as wideband oxygen sensors so that you can keep up with the latest automotive technology and help improve your evidence-based diagnostic skills so you don't become one of those ass hat Parts Chang that honestly couldn't diagnose a diaper rash then uh maybe you should pull up a seat and join me and we can learn this stuff together so come on yeah excellent make yourself at home here have a soda so if you are anything like me and my condolences if you are then like any other shade tree mechanic or home mechanic or serious hobbyist or whatever you are self-taught and that can be kind of a problem because we don't get to go to um Automotive technician technical schools or go to ongoing dealership technician training programs things like that we generally have to rely on our own sources for information um including unfortunately in many cases the internet which I try to use as seldom as possible I mostly like to use my library up here and this is just a collection of a bunch of the books and manuals and even a whole bunch of notes that I've taken over the oh maybe seven years or so I've doing this as a hobby and to kind of make money on the weekends occasionally but there are a couple of things that I highly recommend you get if you are going to work on your own car and that would be these These are actual factory service manuals for specific makes uh and actually model years of particular cars and they will talk about everything you ever could possibly know about um everything Technical and troubleshooting char and all that so if you plan on exclusively working on your own car and really um never wanting to take it to a shop or anything it might be advisable for you to find one of those you can get them on eBay and things now most of my library up here is fairly outdated I think the newest model year that I cover is a 2003 or so and that means I have to unfortunately rely on the internet but I of course never use those uh chat rooms where um a bunch of people that honestly I wouldn't let them fix a samp much less fix my car or going to give advice what I've got here are several articles from some Toyota Engineers um who developed uh their air fuel sensors and also I've got a couple from Wells engineering that as you probably know is a company that makes a lot of Automotive sensors so I figure these will be reliable sources and what I'm going to do for my self-training is what I always do I compile this information I try to make sense of it and then I'm going to apply it to an actual application in an actual car to do a few things because I set goals for my training the first goal is to make sure that I have a thorough understanding of the technology in this case a thorough understanding of air fuel sensors or as I'll use interchangeably wide band oxygen sensors why cars have them how they work how to read them things like that the other goal that I have is I want to be able to diagnose if I have a faulty air fuel sensor or malfunctioning sensor in some way and then the final goal is to hopefully take the knowledge to another level which I often try to do and that is see if I can come up with ways to improve my diagnostic capability by using the sensor as a tool because of my understanding of what feedback I expect from it given certain engine parameters so in this uh video we're going to try to cover all of those today so if you're still interested and that sounds like it's up your alley let's let's get started ah excellent I see you are getting more comfortable or I should say more interested in the material if you're getting more comfortable this up close then it's making me uncomfortable but um before we begin I want to make three really quick caveats to this video um the first one is as I said I am also learning about these while making this video this is part of my training that we're doing here so you will have to take some of the information with a little bit of a grain of salt while I take every effort to as I said use multiple reliable sources for the information and um compile it and everything I don't want to also be one of those people I just complained about where they talk out of their ass and they give false information on the internet I definitely don't want to be Associated like that so the difference is of course we are going to validate this information on an actual application to make sure that the information is accurate but again I may say some things that uh may not necessarily be correct because I too am learning this the second thing that I wanted to point out as sort of a caveat is you are going to need in order to understand the concepts in this video a fairly strong understanding of oxygen sensors your traditional oxygen sensors like your zirconia based oxygen sensors if you do not then this video is likely to be even more boring than it already will probably be but if you are still interested in this then what I recommend is I'm going to put Link in the description to another video I made recently um about understanding fuel Trims and using fuel trims in diagnosis it talks in great detail about the function of oxygen sensors and stochiometry and all of these things that I'm going to use pretty heavily here so that because um most people like me if you're watching this video you're going to be more familiar with oxygen sensors than anything else and I'm using that as the comparison to help with the understanding of air fuel sensors so if you don't have a good understanding of oxygen sensors you may want want to do that before watching the video the final little caveat that I wanted to make is unlike oxygen sensors which for the overwhelming most part there's there's just another exception that's very rare but for the overwhelming most part if you understand an oxygen sensor they're all the same in all years all makes all models but air fuel sensors are not standardized nearly so much so the figures that I give as far as actual numerical information and things like that is going to vary widely between manufacturers between models even between model years there really is very little standardization it seems both from what I've seen personally and in what I'm reading so the point of it is is there will be General similarities but the idea is you'll have to take this information maybe experiment on your own car because if you look at the numbers that I give you and compare them with your car and go oh these numbers don't match do not make a diagnosis that you have a problem with your air fuel sensor then because it doesn't work that way so with that said let's go ahead and get started and the first thing we're going to do is a very brief review of oxygen sensors and then compare them with how air fuel sensors are different and once again I will use of course my amazing artistic abilities in this exercise always go with your strengths but I do hope one day that the um board here becomes kind of an icon on the internet for shade tree mechanic training and uh get some cool like the dry erase board of knowledge or something like that but uh anyway you hopefully are very familiar with this Trace here which would be your oxygen sensor Trace which is going to be the same on all oxygen sensors and again with one exception for a very brief period of time they used these um kinky oxygen sensors uh what were they um titanium dioxide or something where there're a little bit more potentium metric in their Theory so instead of voltages which are shown here it used um what did it use resistance um in response to stochiometric changes but for the most part I believe everybody watching this video should be familiar with this so you've got your stochiometric line at 450 molts and an oscillation changing um richer lean as intended by the PCM um between 9900 and 100 molts and we know that that in a rich condition you have less oxygen detected by the sensor so there's nothing inhibiting the voltage so you get maximum voltage under a rich condition and a lean condition is reported with lower voltages by the sensor and this again is going to be Universal for pretty much any sensor every model every year and everything now the thing is is that we're very familiar with this trace and everything so the first time that you run into an air fuel sensor I know this was the case for me indeed and you see a fairly Flat Line actually a perfectly flat line at somewhere around 3 volts or so uh it becomes kind of an interesting day because of course your first thought is there is something severely wrong with this oxygen sensor in that I'm getting 3 volts from A system that should be oscillating between 100 and 9900 MTS but here I've got a straight line at 3 volts and it seems like nothing you can do in generating richling conditions changes this and you would almost certainly think you need a new oxygen sensor and of course that would be a very expensive mistake because oxygen sensors are considerably less expensive than air fuel sensors and hopefully when you go to the part store and you find out that it's an air fuel sensor you stop and maybe rethink it a little bit but this actually is the new normal for a engine in STO gometry is this Flatline and the thing that um there's a couple things that make this a little tricky actually there's a lot of them so you kind of have to stay with me here one of them is these voltages um these voltages that represent the stochiometric line as I said are not standardized they're different for different models different makes even different model years so what we're going to do for most of this exercise is because Toyota was one of the earlier models to use uh or makes to use air fuel sensors we're going to do 3.3 volts because most Toyotas um you're going to see that and I assume that because these are older uh type sensors that there's more of them out there so there's a better chance that your air fuel sensor is going to match this up but keep in mind that this 3.3 volts may not be the same in your application but this is your new normal now there's other things to get used to as well and one of those is as you hopefully know if you were to have a rich condition with a oxygen sensor let's say that you add propane to the intake then what's going to happen is in the absence of oxygen that is displaced by the propane remember oxygen sensors only read oxygen they have no idea that fuel exists if you were to cause a misfire by pulling a spark plug wire on a cylinder the unburned air and fuel that passes through would actually cause a lean condition on an oxygen sensor why because the oxygen sensor doesn't see that unburned fuel it sees the unburned oxygen which would be much higher than normal from a burn cylinder so it detects a lean condition that's how an oxygen sensor Works air fuel sensors are different we'll talk about that but if you were to create say a rich condition by adding propane to the intake or something you would be well familiar that you would get this Rich line on your oxygen sensor well air fuel sensors report kind of backwards what would happen if you were to add propane to an air fuel sensor is you will actually get uh let's say 2 volts here and let's say four volts here and again these numbers don't mean anything actually they really don't mean anything because the voltages are imaginary I'll talk about that in a minute but what would happen is you would actually start of course going Rich the air fuel sensor does the same as an oxygen sensor just reports the variance from stochiometry but it's going to reduce voltage at a rich condition so in this situation with your air fuel sensor you would be rich and conversely as you know if you were to say pull a vacuum line or something from the intake and you would cause a lean condition and your o oxygen sensor would start leaning out again same thing with an air fuel sensor it's going to detect a lean condition but as you can probably predict now it's going to report that lean condition with a higher voltage so this is lean so as you can see the reporting from an air fuel sensor is sort of backwards from that of the traditional oxygen sensor so this is another thing now that you really kind of have to get used to and it's kind of tricky to get used to and I apologize in the video if I make some fraan slips because I spent seven years doing this and 7 Minutes doing this now but uh we'll do the best we can now I did mention a second ago that these voltages are imaginary so let's look a little bit more into the inner workings of the air fuel sensor and get a better understanding of the differences here so as you know and as I just described um an oxygen sensor measures oxygen and it does it through voltage we know this the air fuel sensor and you may see many different uh names for this air fuel sensor wideband sensor uh constant Lambda sensor all kinds of stuff um may have different names on your scan tool even but it actually uses current to measure the actual air fuel ratio so unlike the oxygen sensor it doesn't simply measure oxygen in the exhaust it actually measures the ratio of air to fuel and it does it using current instead of voltage however it uses very very very minimal currents and it also does it through polarity change so let's kind of examine that a little more thoroughly again with our air fuel sensor we're going to have let's again use our Toyota example so we're going to have uh stochiometry and a good running engine at 3.3 volts and here's our scale here and at stochiometry there is going to be no current no amperage remember this is current not voltage now there is going to be no current through the sensor at stochiometry this is how the PCM knows that the engine is in stoom there was no current detected now in a lean condition and I admit I'm pausing right now because I'm trying to think backwards here but in a lean condition we're going to see an increase in this voltage but what is actually happening is there is now amperage being put through and it's going to be in a positive polarity conversely if we were to say add propane to the intake or whatever and we start going rich and bringing it down here well what that's going to be is a very minuscule current change but this time it will be in the negative polarity and that is going to be a problem that I'll describe later on with these really small amperages but this is how the air fuel sensor is vastly different than an oxygen sensor because you can kind of think of the air fuel sensor not much as a battery that is inhibited by oxygen like a like I usually think of an oxygen sensor but with an air fuel sensor it's sort of like a mini polarity changer kind of thing but there's also um other differences with this too in that the air fuel sensor is more quantitative than an oxygen sensor it actually is better at measuring the air fuel ratio and we'll talk about that in a second but another major difference is these voltages here actually do not exist they're just simply interpreted data that is given for the purposes of the scan tool based on the low current and polarity information so these are actually just interpreted values there really isn't actually a voltage change on this and we'll talk a little bit more about that on diagnosing the wideband sensors so let's um Talk another thing uh about a question you have and that is why do we even have to have these air fuel sensors in the first place why do I have to have this straight line now as sto ometry instead of my usual oscillation and now I've got to think backwards on my rich and lean conditions well the reason is because of emissions requirements and let's take a look once again at The Familiar oxygen sensor here and of course we're very well familiar with this but this isn't actually how the data is given to the PCM it almost looks as if there are degrees of leanness and richness here so that at 450 we know that we would be at sto gometry but if we were at say 600 um Mill volts we would be a little bit rich and maybe at 250 molts we would be maybe a little bit lean it actually doesn't work that way when you look at what the PCM sees from an O2 sensor it it doesn't look so much like this it looks kind of more like this and there's a very narrow range here at stochiometry such that if you notice the PCM can only see the oxygen sensor reporting either rich or lean but it cannot tell how much it's rich or lean it doesn't have like a dynamic capability to determine richness or leanness and because it only has this narrow sensing of the stochiometry that's why you've probably heard of a regular oxygen sensor often being called a narrow band oxygen sensor now let's Converse this with your air fuel sensor so your air fuel sensor again not measuring oxygen but actually measuring the ratio of air to fuel it is going to have a much broader capability and a lot better dynamic range so if we have uh say stochiometry and then we go lean and then Rich well it actually can detect the degrees of that so its range is much broader and that is why this is known as a wide range oxygen sensor and this is going to be far better at determining the fuel trim at optimizing the catalytic converter and at um basically controlling emission so if you have a very very low emission vehicle this is going to be the way to go over an oxygen sensor needless to say that is the trend in the industry and with requirements from the EPA and such so we are going to see air fuel sensors considerably more in more all right so now that we have a fairly decent understanding of how the air fuel sensors function and why we need them and what they do what Their responsibilities are the responsibilities are the same as an oxygen sensor um let's start talking about how to diagnose if you have a problem with an air fuel sensor so one of the things that we know to do with an oxygen sensor is we can reduce conditions where we know that a functioning oxygen sensor is going to behave a certain way and we can measure this using a scan tool or actually even an oscilloscope or actually even a regular digital volt ohm meter you actually can do that you are not going to be able to do that however with a air fuel sensor you are going to need a scan tool and I'm going to explain why because you're never going to be able to diagnose an air fuel sensor unless you've got the right equipment and this unfortunately could be uh kind of a demise for a lot of shade tree mechanics similar to how when we got electronic computer control and fuel injection and oxygen sensors it kind of killed off a lot of the shade tree mechanics from the 70s well you know now if you've got to invest in scan tool equipment and learn how to use it in order to diagnose Vehicles this this could be a problem but one of the things we know is first and foremost being able to detect this trait when we detect this trace on an oxygen sensor we know the oxygen sensor is certainly working we can even further test it um because if we were to say add propane to the intake we know as described that we would get a rich condition and if we were to cause some kind of vacuum leak or lean condition we would see the voltage dropping in an oxygen sensor so we can kind of control it and we can measure that change well the thing is with an air fuel sensor you are not going to be able to do that using a digital volt ohm meter you can create changes in the sensor output based on changing the conditions rich or lean in the engine but you are not going to be able to measure it through any traditional way the thing is with your oxygen sensor you have reasonable voltage outputs no less than 100 molts that you can measure again with even a digital volt oh meter now it's not a pretty way of doing it because uh dvom is not designed to catch a moving Target like that it's going to try to take an average reading of that particular moment but it's always changing so you're going to get your dvom changing all the time to um wish I could draw to all kinds of different numbers you know 28. 7.6 but the thing is if you follow your VM enough you're going to see that it is indeed creating some type of oscillation pattern and of course um if you create a rich condition it's going to kind of Fairly stabilize it's still going to be a little jumpy but your dvom will fairly stabilize at either a rich or lean condition if it's held but you can do these measurements if you don't have really good equipment it's really much better to use a graphing capability the problem with trying to do this on an air fuel sensor is twofold with your air fuel sensor and again let's uh use our Toyota example at 3.3 volts stochiometric and let's go to four and 2 volts and again remember these numbers are going to be insignificant maybe to your car they could be totally different at stochiometry you're going to measure 3.3 volts but remember any changes either lean or Rich do not reflect in a voltage change they are milliamperage changes and we're talking like less than half of a milliamp so the first thing you can't measure voltage there will not be a voltage change these voltage changes don't even exist they're they're imaginary they're just given by the scan tool for the purposes of showing some familiar point of reference so you can't measure it that way but your other problem is that your milliamp scale is going to be too low to detect with a dvom um well certainly at least for mine um and and I'm actually not really all that familiar with DVS on the market I know mine cost like $30 and there's I know there's no way it's going to measure anything even close to this um you you would have to have one that's capable of measuring amperage first of all and then measuring extremely minuscule amounts of amperage now I've seen DVS on the market that cost hundreds of dollars that don't even graph or anything like that and I'm not really sure what the deal is with those maybe those are capable of actually measuring minute amounts of current but even so if that's the case and you have to spend hundreds of dollars on one well I would argue you're better off buying a really inexpensive scan tool and you would actually be better off so that's going to be kind of a problem you are going to have to invest in some type of dedicated equipment to be a able to diagnose the trace on a air fuel sensor now that said provided that you do have the capability to diagnose your air fuel sensor you will be able to do like with an oxygen sensor and make predictions one of the most important things though is like an oxygen sensor make sure that it's fully warmed up before you begin um as you are probably well aware oxygen sensors uh don't start functioning until the engine goes into closed loop that is fully warmed up as opposed to open loop when a default parameters are used and everything but then when the engine warms up it uses the sensors in the engine and the oxygen sensors need to be at like six or 700° something like that before they start functioning and that's the same thing with a wideband sensor but wideband sensors operate at a much higher temperature I think it's something like 1200° something like that but before you start doing testing and using your equipment for measuring the output on a air fuel sensor um make sure that it's warmed up that's really important now one of the things that you are probably familiar with when diagnosing an oxygen sensor is the dead oxygen sensor so that is the oxygen sensor that is just flatlined and it um can be flatlined either rich or lean a lot of times it'll be flatlined lean so this is your 100 and 900 and no matter what you do to this oxygen sensor you add propane to the intake you pull a vacuum whatever it it just doesn't respond now this would be evidence most likely of a bad oxygen sensor especially if it does if this sensor doesn't respond to propane if you add propane here and this sensor doesn't start going Rich almost certainly dead oxygen sensor now you can have a failure like this happen in an air fuel sensor too in an air fuel sensor what would a dead non-responding air fuel sensor look like well most certainly it would be stuck at stochiometry why because remember it's amperage that's measured here and at stochiometry there is no amperage so you have one of two explanations if you add propane or you pull a vacuum hose or you try to do something to change this and you cannot get it off of stochiometric then what likely is happening is you have an open in the circuit CU remember there's no current flowing through it so it's open now that open could be before or in the air fuel sensor but that's one of the things that you want to look for is not immediately jump to a bad sensor but similar to an oxygen sensor test whether you have other electrical problems but typically on a air fuel sensor this is a good indication that you are looking for an open in the system is if you are stuck at stochiometry and there's nothing you can do about it now there's another trick that you can do to validate the ability of an O2 sensor to function and that is of course uh as I said before add um propane and if you add propane it should go rich and if you um induce a vacuum leak it should go lean so you should see those changes very similar to testing an oxygen sensor but there is another way that is actually recommended in this Toyota document that I'm studying here and according to the Toyota document what they suggest doing to test the functionality of an air fuel sensor is to use a snap throttle test and what that means is um 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

Channel: Schrodingers Box

Views: 313,185

Keywords: oxygen sensor, o2 sensor, wideband sensor, wideband oxygen sensor, wideband o2, air/fuel sensor, A/F sensor, equivalence ratio, lean engine, rich engine, air fuel mixture, scan tool, auto enginuity, autoenginuity, diagnose oxygen sensor, diagnose air-fuel sensor, air-fuel sensor, Subaru o2 sensor, toyota oxygen sensor, p0174, p0175, check engine light, scannerdanner, eric the car, air fuel ratio, test o2 sensor, how to test oxygen sensor, test wideband sensor, yt:stretch=16:9

Id: XQYDwIWS6Ho

Length: 29min 59sec (1799 seconds)

Published: Fri Mar 21 2014