O2 Sensor Basics - EricTheCarGuy

[@johnd942]

If only all KZbin presenters could follow your lead; keep it short and simple (K.I.S.S). Very well done Eric.

[@PatRiot-]

Lieutenant colonel I knew had a saying of Keep it simple stupid Always worked out

[@daniejames2591]

Hey Eric, I been watching your vids for a a while and you saved me not only a headache but money I dont have. Yo simply rock and thanks for the education.

[@MackFFT1]

I guess what I am trying to say is due to your videos and your explanations I have learned a lot and am actually investing in tools to fix my car and really getting motivated to make a career out of fixing cars. It feels great to be able to do something that other people get paid lots of money to do. Again thank you and I really appreciate the time you take to do these videos.

[@jackryan4313]

9 years later. What's up? You still doing your own thing for your cars? Did you ever take up car stuff professionally?

[@ericthecarguy]

@alexroufs I'm glad to help. I really appreciate your comment as I work pretty hard at making my videos worth watching, thanks.

[@ericthecarguy]

I plan to do just that but if you need the information now, you are looking for a signal from the O2 sensor to fluctuate around 0.50 volts as the car is running. You can do this using a DVOM set to measure voltage with one lead on the sensor and the other on a good engine ground. Thanks for the comment.

[@ForTheManDIY]

Thanks for all the great videos. I would like to mention that the optimum O2 sensor signal is not 0.5V, but instead swings from below 0,2V to above 0.9V. This is required such that both catalysts are functional within the catalytic converter. One catalyst only works below 14.7:1 AFR and the other only works above 14.7:1 AFR. This is a minor yet very important point. Many falsely believe that the computer just can't keep up and hence the swing. Actually the swing is for proper cat operation.

[@ericthecarguy]

@Drudy90 Lean codes are almost never the O2 sensor. It's usually an engine performance problem such as a vacuum leak or sometimes an exhaust leak. You might benefit from the video I did on "Power Balance Testing" too as well as finding a vacuum leak.

[@ericthecarguy]

@td1238 I think you hit on an important point and that is working on the car that your working on is more like an 'art' rather than an absolute which is what I consider working on modern cars to be. With the older engines and carburetors you had to work to get things right, now you just replace parts. Sounds like you know what your doing though. Thanks for your comments.

[@ericthecarguy]

@SICKSxNINE Glad to help, thanks for the comment.

[@ericthecarguy]

Excellent question, I think it will make a nice topic for a future video. For now to answer your question, on a V6 engine there are at least 2 sensors, one for each side of the engine, bank one is the side of the engine with #1 cylinder. Your jeep would have a straight 6 I believe, in that case bank one would be the sensor closest to the engine. Good luck and thanks for the comment.

[@ericthecarguy]

@blind898 Great question. The secondary O2 is just for monitoring catalytic converter efficiency and does not contribute to the fuel mixture calculation. The secondary O2 is mounted either inside or after the cat, the computer compares the readings of this sensor with the front sensor to gauge cat efficiency.If the front sensor and rear sensor read close to the same the cat is not working. You should see the secondary sensor remain pretty much constant while the front will fluctuate when good.

[@ericthecarguy]

@michaelmonsod That is probably my favorite thing in the world right now, helping people save money. Thanks for the comment.

[@HamzaKhan-dk9qr]

Eric what if your post oxygen sensor is not connected. I actually bought a swapped Vitz/Yaris from 1.0 to 1.3. i noticed that it's post oxygen sensor.is not connected

[@ericthecarguy]

I keep working on it. I'm not quite to the software/hardware levels that they are yet but I'm getting better about creating these things from scratch. Your comments are always appreciated. Perhaps one day I can create a marriage between art and teaching thus completing my purpose in life.

[@ericthecarguy]

@Brendon00000 Yes the O2 sensor is the primary sensor used by the PCM to calculate the fuel mixture after warm up, often installing a new sensor will do all of the things you describe. Thanks for the comment.

[@ericthecarguy]

@Sanjeai Yes it should be located in the 'A' pipe just off of the engine before the cat, it might be in the manifold however I don't remember exactly, look in the exhaust as close to the engine as you can for what looks like a spark plug with wires coming out of it. When you find it to remove it I would cut the wires off of the sensor and use a 7/8 socket or box wrench to remove it rather than trying to remove it with an O2 sensor socket. Good luck.

[@MotorScotti]

Eric, your older videos still rock! Thank you for the short amd snappy explanation!

[@ericthecarguy]

@demotorduvel I plan to at some point in the future. Thanks for the comment.

[@ericthecarguy]

@frank0067 Those are for the heater which I hope to cover in future videos, only 1 wire will be the signal wire and to be honest the best way to see it is with a scan tool because you can check it while sitting in the drivers seat. Scan tools that show live data are pretty affordable these days.

[@ericthecarguy]

Thanks. I've been working on my illustration skills, it's a cross between Photoshop and Apple's Motion. I think it works to help describe complex operations. If I were to do it again I might slow down the dialog though.

[@ericthecarguy]

@PlusOrMinusOne Your welcome, thanks for the comment.

[@ericthecarguy]

@hiks1969 It is a Denso but it was bad that's why I used it in the video. Sorry I don't have any that are good that I could sell.

[@ericthecarguy]

@frenchokie You get more power out of a carb at least if it's set up right. Thanks for the comment.

[@ericthecarguy]

@chackers Lean is not enough fuel OR too much air, rich is just the opposite. The sensor has 2 parts, one exposed to the outside atmosphere (those little holes around the top by the wire) and the other end is placed in the exhaust stream. The bigger the difference in O2 between the outside air and the air inside the exhaust the greater the voltage produced by the sensor, in short, rich means (less O2 in the exhaust) voltage close to 1V and lean means a lower voltage is produced closer to 0V.

[@ericthecarguy]

@evernet01 No, the heater is part of the sensor assembly so you would have to replace the entire sensor.

[@ericthecarguy]

@cwilkins318 Misses under load are often the result of an ignition problem but not always. If you have a check engine light on then that is where you should start with your diagnosis, pull the code and follow the trouble shooting for that code, once you have done that check to see if the problem is still there, if it is then perhaps check the wires and the rest of the ignition system. Good luck.

[@ericthecarguy]

@sonicthehedgehogca I actually plan to do an entire series on emission controls and their function at some point.

[@ericthecarguy]

Thanks for that comment, I try and post once a week, usually Wednesdays.

[@ericthecarguy]

@Turbotrips I didn't say that it measures the O2 in the outside air but rather that it produces voltage based on the amount of O2 in the outside air as compared to the O2 in the exhaust. The difference in O2 causes electrons to flow and produce a voltage that is proportional to exhaust O2 content.

[@ericthecarguy]

@ramrice That engine does not use a MAF so you can rule that out. The P0401 is an EGR flow problem, I know you mentioned you cleaned the EGR port but what you really need to do is clean each of the individual runners going into the intake, see the video I did on cleaning EGR passages. Start with this code and reset it to see if the other codes come back as they do not mean the O2 sensor is bad but rather it detects a problem with the fuel mix.

[@ericthecarguy]

@founditnow54 Toyotas are famous for this, first I cut the wire and use a regular socket or the box end of a wrench not an O2 sensor socket, I normally use heat but there are still occasions where the threads become damaged during removal and require re-tapping.

[@ericthecarguy]

The PO302 is a misfire code for cylinder #3, you might want to check the plug and injector for that cylinder. Thanks for the comment.

[@ericthecarguy]

@ip161314 Yes the 4 wire works the same way the other wires are for the heater that brings the sensor up to temp quicker during warm up.

[@jeremiahmoyer8876]

Helping me cram for midterms, love it

[@ericthecarguy]

@michaelmonsod It is most likely the sensor but it could also be a wiring problem. I like to verify it's operation or non-operation before I replace a sensor, a quick look on a scan tool is all that I usually need.

[@ericthecarguy]

@PigE911 Thanks for the comment. What exactly were you looking to find out about with spark plugs?

[@td1238]

I actually came up with a formula for figuring out metering jets based on the viscosity and stoichiometric ratio for ethanol, when used at 10%, and the formula came out with a similar jet number, but in real life the amount of ethanol varies from 10% to less than 10%. The oxygen sensor helped me fine-tune everything so that I'd cruise and drive in the 80s, and when the enrichment jet kicked in the voltage would almost max out, but not quite or else I'd get sooty spark plugs.

[@ericthecarguy]

@krazy8tattoos Sorry, I just don't have the space here to go into all the intricacies of the combustion process, stay tuned for future videos. BTW it might be that nothing is wrong and that's the way the engine runs.

[@MackFFT1]

Hello Eric! Great videos brother. I appreciate the time you take in doing these videos. I just replaced the water pump and timing belt on my 91 Legend and took it for a test drive and I noticed the car consuming more gas than usual. I retrieved the codes and after speaking to a Mechanic he told me that both o2 sensors were bad. Codes 41,44,17.

[@ericthecarguy]

@frank0067 You might want to re-watch the video, the sensor is exposed to the inside AND the outside air, that is the purpose of those holes on the top of the sensor, there is not separate sensor it's all the same one.

[@ericthecarguy]

@JotaJotaHJ If the sensor has more than one wire one of them is actually powering a heater that is used to get the sensor up to temperature more quickly, those are mostly 12 volts however, or you might be on the wrong wire at the ECU, most reference voltage is 3-5 volts, you could have been on another sensor wire.

[@ericthecarguy]

@td1238 Actually it does measure rich by default, if you know the amount of O2 in the exhaust you know how the engine is burning. .5V would be ideal for a fuel injected car but carbureted cars will run richer, if you want to set your carbs do it with a vacuum gauge as that is a much better method than reading an O2 for a carbureted car as it's hard to get the adjustment right as you have found. It also has a lot to do with your cam and how the rest of the engine is set up.

[@ericthecarguy]

I stand corrected.

[@ericthecarguy]

@sxr951 You might start by pulling any codes stored in the computer, if you don't have any codes go for the general tune up stuff and check the mechanical condition of the engine. Don't just blindly replace parts as that gets expensive.

[@ericthecarguy]

@nickernosher That is exactly what it should be doing, when they get old they tend to switch a lot slower and are less effective at maintaining optimum fuel ratios as a result.

[@ericthecarguy]

@francisco8036 Not exactly, keep those little holes in the top of the sensor away from grease or other contaminants especially silicone as that will damage the sensor.

[@ericthecarguy]

@alexroufs I have a couple actually, in fact I have videos covering all the things you mentioned. I hope to better organize them into categories soon but for now you can just do a search for the video you are looking for with EricTheCarGuy before whatever your searching for in the search box at the top of every YT page.

[@ericthecarguy]

Probably not a bad idea. I will have another video in the future about replacing them, a special socket may be required, you might get away with just a 7/8 wrench though.

[@ericthecarguy]

@pCneter I used motion graphic software to create the animation in this video if that's what your asking.

[@ericthecarguy]

@Brendon00000 Did the sensor actually fix it or was there some other problem that was causing the mixture to be wrong?

[@davel6024]

One very missed issue here with 02 sensors these actually breath through the wires so just a heads up for those who didnt know this very important when and if you use electrical tape (some do) if so dont because the fact they breath through the wires is very important. Thanks eric for the new format different but will adapt to it i think lol... Stay dirty folks ~Dave

[@wmichaels362]

Also, soldering an O2 wire will block the path for the reference air.

[@td1238]

I went over every other possibility before coming to the conclusion that the jet needed increasing. I remember that when I first bought my car in the 1990s I could adjust the carburetor fine, but then when E10 moved in sometimes I could adjust the carb perfectly, and sometimes I'd have to turn the idle jet way out to get results, and I tried several carburetors with the same results. I also rebuilt the engine at about 100,000 miles, so guides, valves, seats, and rings were perfect.

[@ericthecarguy]

@DSchruteBeets The O2 is still good but the heater that is designed to bring the sensor up to temp has failed, this will make it so that it takes longer for the sensor to warm up but it will still work when it does.

[@ericthecarguy]

@Super98mustang OK, there are about 10 codes for an O2 sensor but not all mean a bad O2 sensor some indicate another problem that the O2 sensor is detecting. What code(s) are stored now if any?

[@ericthecarguy]

@spelunkerd Before OBDII this was the case however the newer sensors are much more accurate and with faster ECU's it's easy to see if a sensor is not performing correctly. In fact before OBDII it was common practice to replace an O2 after about 60K as part of a "tune up". You really don't need a lab scope to check them however just a good DVOM.

[@ericthecarguy]

@KaldekBoch My videos are full of happy people, I don't explain why, they just are. Thanks for the comment.

[@alexroufs]

Hi Eric, Alex again this is exactly what I refered to in my previous comment. I can try to look for this information in a book or talk to a so called mechanic (I know there is plenty of good mechanics in the world but not so many in that part of the world that I like to call second home) and I have no clue what they are talking about. This is simple and straight forward more over it sticks!!!!! I always wanted to take a course in car mechanics...I found it

[@ericthecarguy]

@blind898 Sounds like someone made a modification so that the light was not on after they "modified" the cat. Not sure what you have there without getting my hands on it but if you want to say legal you will probably need a cat and O2.

[@rayrooney1]

who'd win in a fight eric the car guy or scotty kilmer.

[@hendrixtarantado2114]

Lol.😂😂 Out of all the car related shit u could've asked.🤣 This is just my type of humor...👊👍✌️

[@theblueoval3029]

Eric for sure ol Scotty has to let out a grunt to tighten a park plug hahahaha

[@AFatherToTheFatherless]

@@theblueoval3029 LOL

[@brooksbourkney659]

Chrisfix would lol

[@hisheeelijah1482]

Nah scotty would with his wailing swings.

[@ericthecarguy]

@Tagard1995 I have no idea but I suppose it would as it's really the difference in O2 content that makes it work, I don't believe it is dependent on pressure.

[@ericthecarguy]

@evernet01 I believe that code is for the heater inside the sensor itself, if the wiring is OK it's probably a bad sensor as the heating element is separate from the sensor output.

[@Super98mustang]

@ZukiBiker13, I had it checked out and it was the 02 sensors. The place the i got it checked at said that the 02 sensor would drop a signal at a random time for no reason. When it does that, it would flood the engine with fuel causing it to sputter and stall .The computer would think the car was lean because it was not getting a signal from the sensor and that would cause a code to pop up saying that the mixture was too lean but it wasn't. I got new 02 sensors and now the car runs & idles great!

[@ericthecarguy]

@Super98mustang Not really, the O2 sensor for the most part is for fuel trim, if the computer senses that it is out of range for an extended period it normally turns the check engine light one and ignores its input. Do you have a check engine light on? If so, what code?

[@johnbecich9540]

This is an excellent, to-the-point primer on that oh-so-important sensor.

[@ericthecarguy]

First, don't make assumptions, gets me into trouble all the time. If you suspect a bad O2 you need to verify that with evidence meaning you need to check it's output while it's running to see how it is operating, if it's out of range then sure replace it. After a time they do get old and don't work as well as they did, some would say replace them as part of a "tune up" but you might just be replacing parts. BTW what your looking for is a reading near .5V which is neither rich or lean.

[@jackryan4313]

I forget how much technology has progressed...come tell me that you have a CEL and I'll just plug into your car and tell you everything you need to know, and then I'll be able to tell you what everyone else did to fix it...damn, in today's age, 13y is more like 30 if you're thinking about tech from the 40s/50s😂

[@ericthecarguy]

@infamisss1 Rear O2 sensors monitor catalytic converter efficiency and don't effect fuel mixture. If you want more power they only real way is to modify the engine and the fuel map of the PCM accordingly. Other than that you will just be confusing the existing system and loose power and increase emissions. Modern cars are set up to discourage modification.

[@ericthecarguy]

@AirCrashMayday It doesn't however if you run methyl alcohol past it it might.

[@ericthecarguy]

@hydraz06 Not sure really but it reacts with O2 and produces voltage based on the amount it's exposed to.

[@ericthecarguy]

@lwgraves I see where your going with your statement however I stand by my statements because this is a video covering the basics of O2 sensor operation NOT AFR sensors or any specifics of either. Thanks for your input.

[@courtneyclarke9139]

I have a problem with my car there is no check light when I turn the key to the on position and the car wont start ,u have any idea what could be the problem

[@ericthecarguy]

@EncinitasLokal That is what the code is for but check the O2 sensor readings to make sure that it's not an O2 sensor problem.

[@ericthecarguy]

@bw110719 I'm not sure you will have any real gain from just replacing them but it can't hurt, I think the most you will notice is slightly better fuel economy. If your looking to get more performance start with the basics like a good tune up.

[@ericthecarguy]

@desisandhuman It's hard to say without getting a look at it for myself but if it occurred after you put those plugs in you might consider putting the OE back in just to check if that makes a difference. Using performance parts in a non performance application is often not the best way to go in my experience especially on newer engines.

[@ericthecarguy]

@TopGearrules The system will not read information for the O2 till the engine is at operating temp so the O2 is probably not at fault for the cold idle problem. I would look for connectors or something that might have been moved or damaged during your repair. In other words check your work as you might have done something accidentally or the sensor may be faulty hard to say really.

[@axistorr]

Eric the car guy your a god amongst men!!

[@ericthecarguy]

@joejeep03 Not all O2 sensor codes mean that you need an O2 sensor, some of those codes mean that the O2 is seeing something that is not right. Really depends on what code but you may have fixed it with your tune up as you said.

[@ericthecarguy]

@ir1337zor I recommend getting the sensors into the stream as they will read better that way. I don't recommend running without a cat however. You will probably get a code P0420 but you can ignore it since your not running a cat.

[@ericthecarguy]

@IDONTKNOWIT21 Probably one of the most important sensors on the car is the O2 sensor as far as fuel mixture is concerned so yes you need it for good fuel economy. If you run it without a cat however you will still have a check engine light however not to mention it would fail an emissions test.

[@ericthecarguy]

@jambe1234567 It monitors catalytic converter efficiency which is an integral part of the emissions system and if your going to pass an emissions test all systems need to function as designed.

[@AmandaDelight]

I see this as a great way to combine that creative outlet with your wealth on knowledge! Its great! Has a very professional feel to it! God, if you do enough of these, you could sell a finished product to tech schools, or even an independent study guide...you might be on to something here!

[@ericthecarguy]

@MrPoloboy25 I would be checking the operation of the IAC valve as well as look for vacuum leaks just to be on the safe side.

[@ericthecarguy]

@billywaltmon That's really not possible, it's much better to replace them as they get old and don't work as well, not as a result of getting dirty but rather as a result of getting old. Aside from that O2 sensors are very sensitive to solvents so you would probably do a lot more damage than good by cleaning them.

[@ericthecarguy]

@mayers000 Thank YOU for the comment.

[@ericthecarguy]

@rock21586 I don't see why not, it's really no different than changing any other exhaust component. Look for a "bulge" close to the front of the engine in the exhaust system, this is usually the catalytic converter.

[@ericthecarguy]

@scyllis I'm thinking you did your test incorrectly. If your O2 was bad on that car it would set a code so your only replacing them because you want to. As for the P0420 get your hands on a scanner that gives you live data and compare the front O2 reading to the back, the back sensor should stay fairly constant around .5V while the front should switch quickly, if the rear also switches quickly and does not stay fairly constant then the cat is bad and should be replaced.

[@ericthecarguy]

@frenchokie Yes, O2's are very sensitive and would probably foul if you ran oil past it like that, besides what good would it be for that engine?

[@Rrm-br5ku]

You're amazing!!! You always find a way to explain things in a way everyone can understand.

[@larryhernandez5062]

Excellent . . . Stay Frosty . Basics

[@ericthecarguy]

@tigerhorns The black smoke may have nothing to do with the O2 sensor, in fact it could be something else altogether. If you have a check engine light for an O2 then I might pursue that but it could just as easily be an ignition problem or some other electrical issue. I'm not a fan of cleaning engines as I've seen lots of problems pop up similar to yours after cleaning.

[@ericthecarguy]

@jambe1234567 There is no physical difference in the sensors and you are correct it's only purpose is to monitor catalytic converter efficiency which was mandated as part of OBDII. It has nothing to do with fuel economy but if you suspect a bad cat you can compare the 2 readings and see how the cat is doing, if they read about the same then the cat is bad, if the post sensor remains around .5V then the cat is working fine.

[@ericthecarguy]

@OtherVincentLee Actually yes as the O2 would be displaced by the methane thus indicating a rich condition.

[@ufartface]

i thought is was ethanol in fuel not methanol

[@YeTenuousUmbrae]

eric the car guy. much better than another eric cartman.. hur hur hurrr

[@ericthecarguy]

@savuisai That doesn't sound like an O2 sensor problem but rather an oil control problem, I suspect it's the oil control rings. To fix it you will need to repair or replace the engine. A compression test will help confirm this, I've done a video on compression testing if that helps.

[@ericthecarguy]

@11skidoo232 That engine has more than one O2 I believe, one in each manifold. Your engine probably wouldn't suffer without a cat however it is illegal in just about every state to remove one permanently.

[@ericsinct]

thanks for all your help and suggestions. we need more honest mechanics like you...

[@Discretesignals]

If the O2 sensor isn't working, as it isn't switching, usually the ECU will set a trouble code and the fuel system the O2 trims will go into open loop. Sometimes faulty O2 sensors can stick high or low and cause drive-ability issues. Good idea to perform an O2 sensor response test if you believe the O2 sensor is sticking.

[@jygogaming3550]

My o2 is stuck at 2.3volt running rich

[@YouTube.TOM.A]

Obtain the wiring diagram for your vehicle or go to the junkyard and find a vehicle like yours [same year generation and engine] look at the colour of the wires LEADING to the O2 sensor CONNECTOR and trace it back to where it joins the larger wire bundle,[which leads back to the engine computer]. most likely the wire [s] if cut were cut outside of the big wire bundle. you may also cut out the wire[s] and connector from the junkyard and re solder it [them] to your car using the wire color codes

[@YouTube.TOM.A]

Its possible that some modifications were done to your engine. Sometimes oxygen sensors are removed and electronic chips added to increase the power output. go to the dealer or use alldata and verify the location of the sensor. check the fuel trims,mass airflow, engine coolant temp, fuel pressure and all streaming data and evaluate engine condition. don't assume the poor fuel economy has only one cause. consider obtaining a PCM [power control module] and new exhaust pipe with O2 sensor opening

[@ericthecarguy]

@Itsmeeman1 It would not go into closed loop meaning that the computer would probably go into a 'limp in' or 'fail safe' mode and performance and gas mileage would be compromised as a result.

[@YouTube.TOM.A]

Go to the dealer or parts store and compare the part numbers .sometimes the part numbers are the same. the sensors do the same thing internally but one is moved further away form the exhaust and monitors the viability and functioning of the catalytic converter.

[@ericthecarguy]

Still won't work, the ECU monitors efficiency on all cats, that's why there are so many. I have heard of some aftermarket devices that are suppose to help eliminate your particular problem but I've never used it. Google O2 bypass or something and see what you come up with.

[@ericthecarguy]

@MyHurtlocker If it's a 2002 it would set a code for a bad O2 if it was bad. You might want to look elsewhere for the problem, I would start by hooking it up to a scanner and reading the data that the computer sees to look for any anomalies that might indicate the problem. Any good technician should be able to do this.