What is Oxygen Sensor Bias Voltage? (an SD Premium video)

[@scottdoney6926]

Hi Paul I work in Australia as a technician of over 44 years experience and have lately move to trainer I tell all my students to view your classes they all are amazed that we don’t teach like this in “Aus “ And that electrical is only for sparkles this is so not true in cars of today love your work keep it up I teach a lot of your work and my own captured data and history again great job !!

[@ScannerDanner]

Awesome! I'll be visiting the Melbourne area (I think) in April of 2020 for some auto stuff.

[@scottdoney6926]

ScannerDanner Hi mate love to catch up while your in Aus could offer some free accomodation if your coming north to port Macquarie NSW ANY TIME I myself am heading to Melbourne/ Tasmania in April 2019 only miss you by one year anyway safe travels and love to catch up

[@rrmech11]

Hello Paul Excellent teaching of Bias Voltage. One viewer brought up the topic of worksheets. Great idea. People around the world would truly benefit.

[@ScannerDanner]

thanks Richard!

[@bumbaclot18]

Thank you, Sir. You described my problem exactly. o2 heater circuit malfunction code 41, heat element in sensor checks out, wiring checks out. Factory flowcharts don't give signal testing procedures or values and, whats worse if you follow flowchart to end it suggests bad ECM. I couldn't convince myself to throw parts at it (new o2sensor) without evidence it was bad, had started to believe I needed a new ECM. Edit: forgot to mention going to try this out tonight. Working on a 94 Acura Integra.

[@davesministry7789]

Excellent again. This info will save a lot of time and money. Thank you. Especially from my church people who will not be buring things they don't need. Thank you from all of us.

[@ScannerDanner]

Thanks brother

[@nickayivor8432]

Good Evening ScannerDanner take care and have a great day ScannerDanner 👍 Great tutorial thank you 👍 From Nick Ayivor from London England UK 🇬🇧

[@ozzstars_cars]

I learned something new today. I never knew how Chrysler O2 heater circuits were monitored until today. I think it is terrific how you found this info out Paul and shared the knowledge . Fantastic video.....as always. Take care man

[@ScannerDanner]

Thanks man. Check out the videos I have posted in the description of this one. It will be even more clear.

[@gladmarchatlein8164]

Awesome and Priceless way of teaching others sir ScannerDanner!....Blessings!

[@ThunderbirdRocket]

Excellent topic ! Fantastic lesson !! Thanks 👊🏼

[@areid1440]

Excellent teacher!!!!!

[@wyattoneable]

Boy you weren't kidding about seeing the bias drop in real time to help understand the circuit!

[@ScannerDanner]

cool man

[@pedrolriveranegron5178]

Excellent Tutorial!!! Very detail on how to test o2 bias-voltage.

[@ScannerDanner]

Thanks brother

[@thesetruths1404]

FYI, my 2003 Mitsubishi Montero 3.8L seems to have a super low bias voltage of 0.11 volts (yes, 110 mV). Both oxygen sensor harnesses read the same on the corresponding harness pins. I couldn't find this on any Internet source...probably because most 15+ year old Mitsubishi are in junkyards, in USA anyway! Lol...but I like mine! Now if I can just figure out why it sometimes refuses to start when it's in the middle of winter. All I have is an occasional P0171 code (bank 1 lean), and an occasional P0431 (Bank 2 CAT bad efficiency). Both downstream sensors are showing ok (0.2 to 0.8v). Bank 2 downstream sensor shows fast-moving from 0.2 to 0.9V. Bank 1 downstream is steady at 0.8 to 0.9 V. My bank 1 STFT is usually out of spec (usually +13 to 25%), while Bank 2 STFT is usually ok, between -5 and +5%. I took voltage readings from each upstream sensor when it was hot and voltage matched what the scanner app said it was. No vacuum leaks I can find using a half can of carb cleaner. It would not start from January through mid-April and once it warmed up outside to 50's F something allows it to start and run fine! Perplexing...

[@NobodyAskedForThis]

Awesome video. Practical checks that most manufacturers don't tell you. When checking circuit integrity wouldn't it make more sense to unplug the sensor and use the circuit ground to short the signal wire rather than using body ground? Using the circuit ground when shorting the signal wire verifies both the signal circuit integrity and ground circuit integrity at the same time. Thanks.

[@johnnyheckard7185]

J

[@williegillie5712]

I know a Harley is a status bike but why would anyone wanna sit on something that idles so rough you can see the mirrors shaking. Could just as well be riding an old John deer model A tractor. I like a smooth running bike. Just my preference. Nice smooth idle and a great power curve when accelerating. Good lesson great explanation of how the O2 sensor heater circuit works.

[@michaelodell5296]

Hi Paul, This is unrelated to this video but I could not help my self from asking. You videos are some of the best I like how you cover all the aspects of the issue at hand. Nice to see how complete you attack a problem. I find the best part of your videos is when you teach your self! Keep up the excellent work! I was wondering, could you do some ABS Traction control videos? I would like to see how to test the system electric and mechanical. Bleeding the system is a challenge as well. Some systems also integrate the steering angle sensor can you explain why? One last thing the CAN BUS system HI Low testing how to know if its talking to the PCM or the PCM to the ABS module. Thanks Michael

[@ScannerDanner]

Thanks so much! Here is a playlist for some ABS stuff kzbin.info/aero/PLAFYVCyenqcoLcXnSf8IW23v-zoJfAi9- And for sure I'll post videos for the other things you mentioned as I see them.

[@rcchar]

Paul I do not think ice on the O2 sensor will hurt it, I lived in Minnesota and in the winter it can be -50 with the wind chill. Plus if you park outside in the snow it gets right on the O2 sensor. Cooling the sensor down fast.

[@ScannerDanner]

I was just worried about the sudden rapid cooling but your point is a good one for sure.

[@jdean399]

That is a really nice bike, great video, looking forward to those worksheets becoming available. Take care

[@ScannerDanner]

Thanks Jonathan!

[@ColeTanner88]

Do you have any videos teaching about the newer A/f ratio sensors on Fords? I believe they're 5 or 6 wire and are using a bias. Ive not had time to sit there and play around with 1 yet. The ones I've had have been hard to get to the connectors and of course the exhaust is piping hot. Ive been checking heater circuits with a test light and then unplugging the sensor to check for 2.5v due to seeing that on others. I'm not exactly sure how they work with, I believe they call it, a nert cell? Would like to learn more about them though

[@ScannerDanner]

Not on the design you mentioned but I do have a few wideband O2 videos. Search "wideband" on my channel. Thanks!

[@ΓΙΩΡΓΟΣΓΑΛΑΙΟΣ-λ9θ]

Very good video if the teachers could teach like you People will be better we thank you

[@timowallin8020]

yes thats(on bike) the Bias i wanted to see(on your last video), so i wouldent need unplug that wireharnes to clear it in my head ;) Anyway lower then 1 volt Bias. man i need to take out my tools moore and see do we in here have those to help as.... Thanks Paul for the folowup video and Help!

[@ScannerDanner]

Yeah, in hindsight I should have unplugged it for you guys but I will tell you, it would have been the exact same reading as a cold sensor. Measure the resistance between the signal wire and the signal return wire sometime on a cold sensor. It will read an open circuit

[@timowallin8020]

yes that what i would like to see on our cars in Europe. As you unplug a sensor or so a Bias voltage. so you dont look for it to change how the engine or what ever you have do things but to see the wires to the brain" is OK at least if they dont need to handel a load...

[@timowallin8020]

Anyway i see more and more me to get my Pico out even on "cheap stuff" :)

[@ScannerDanner]

Exactly! No need to do resistance measurments when you understand bias voltage

[@Sid9397]

If your working on a vehicle with multiple O2's , Do you need to unplug all the O2's before testing them individually ? Referring to the voltage drop using your finger .

[@Discretesignals]

No you don't. Each O2 has its own signal circuit and voltage data PID.

[@spelunkerd]

I think the reason you can get away with applying 12V through your body to a 1V sensor circuit is because the resistance is so high, current is miniscule. The damage inside the pcm comes from power, the product of current and voltage. Although voltage is 12 fold higher, the current number is so tiny the PCM never sees enough power to fry electronics or fingers. On a plot of resistance against current (or power) the only way to deliver significant power is with high current. Comparing similar plots of current against resistance for two hyperbolic curves of 12V and 1V, the two curves are remarkably close together on the far right side where resistance is high.

[@ScannerDanner]

It actually goes beyond any external resistance. It is the internal resistance of a signal circuit on an input sensor in general. For example, I have seen the 12v heater positive shorted to the O2 signal wire and it DOES NOT hurt the computer. Fix your short and you are good to go. It may hurt the O2 sensor, but not the computer. I have a case study on this on SD Premium on a Lincoln.

[@spelunkerd]

Excellent point. Engineers get a lot of criticism in retrospect, but their effort is often not appreciated when they do something right. By designing huge internal resistance, they plan for the misadventure when stuff happens. It's another one of those invisible safety nets underneath. Thanks again for an outstanding video, Paul.

[@ScannerDanner]

No problem and thank you for the comment! It looks like you channel is really growing too. Congratulations my friend, good providence to you.

[@gmtech2012]

The only thing I'm wondering is that you could have one strand of wire carrying that bias voltage to the sensor. You measure bias and everything seems fine.

[@thesetruths1404]

I've got a 2001 Honda CRV that I measured the white oxygen sensor wire on the harness side, with the sensor unplugged, and it was showing 1.28 Volts. The car was warm. I have a P0131 code with hard starts and stalling indicating the O2 sensor. I confirmed the 1.28 V with two multimeters. When I monitor the sensor with the code reader and the multimeter it seems to work ok when cold but as soon as it's warm the voltage drops to .1 to .2 at most, the car will sometimes try to stall, and the code will occur. So it seems to be a failing sensor. But I wanted to be sure it's the actual O2 Sensor bc I hate replacing good parts. I also unplugged the vacuum line to the PCV and it started revving the motor up and down between 1000 and 2000 RPMs. This 1.28 V doesn't seem to be right though. What could cause that?

[@ScannerDanner]

This is normal. It is called a "bias voltage" and is used by the ECM for diagnostic purposes. What you are describing is NOT an O2 problem. Quick lesson: 1. An oxygen sensor is not even being used for at least the first 30 seconds from start up on a cold engine. Do you understand why "hard starts" cannot be the O2 causing this symptom? :-) 2. When the engine warms up, you are seeing an ultra lean signal on the O2. This could be a bad O2, but see point number 1 and the fact that you said it seems okay cold, then when it warms up you see the signal drop to .1-.2. This tells me the O2 is fine and you have an actual lean condition. (yes it will set that code). This screams a fuel delivery problem. MAF sensor test and then fuel psi must be confirmed next.

[@thesetruths1404]

@@ScannerDanner thanks! I mis-tested it. Bad wire connection or ground. Went to it directly with voltmeter leads and battery negative and it read 0.40 V, as it should.

[@balafulama6005]

hey paul, so what is the difference between pull up/ pull down and bias voltage? thanks

[@ScannerDanner]

To lengthy of a discussion for text on a screen. Go to my chapter 2 playlist right here on KZbin, then when you're ready, my chapters 2 and 3 playlists on SD Premium from my website. I'll do my best to answer when the question is more specific if that makes sense. Thanks!

[@Fran-yg4jp]

Does anyone know is there away you can test a 02 before you put in a vehicle? to see if you have bought a good 02

[@codywichman213]

I had a dodge Dakota 4.7 yesterday. had no power to the o2 heater on bank1 sensor 2. good powers and grounds to each of the other o2s. using the diagram I followed it to the ecu. on this design the ecu p.w.m the heater for all of the o2s. it has an asd sense circuit also. this car had burned the harness against the cat melting all of the o2 wiring together. my conclusion after back probing the computer was the driver had failed from a short to ground.

[@ScannerDanner]

usually once you fix the harness, everything comes back to life. Not the case for you?

[@ياسرعليمحمد-ابوابراهيمالطائي]

My o2 sensor downstream changes readings with change of speed R P M of engine & with change of fuel ratio -the problem is the bais voltage of town and country is 2.5 voltes .the senor voltage comes down to .77 V and never goes to .45 V !THAT gave me P0137 and smelly exhaust -Can I Modify this range to the correct values?THANKS.

[@OffroadGeekDxb]

Question, my B1S2 fluctuates but shows negative readings between 0.2 -0.8. any suggestions on what could be the issue?

[@danjensen100]

When you are emphasizing that the signal is "weak" (the 5v bias), then showed how you can drop it by touching it with one hand and ground with the other hand, what constitutes it as "weak"? Just the fact that the voltage is only 5v and not 12v, or is there some other factor that makes it a "weak signal"? Could you drop any 5v supply by touching it with the other hand on ground?

[@ScannerDanner]

No to your last question which should answer your first question. Or these videos may help - What can cause an O2 sensor to read near 5 volts? (Chrysler bias voltage) kzbin.info/www/bejne/rGm7o4BjbKeohck - System Too Rich P0172, P0175 from a blown O2 heater fuse (Jeep) kzbin.info/www/bejne/iXbYeKednL90rNE

[@rjdownie161]

So on my 2001 Dodge 5.9liter the O2 bank 1 sensor 1 Heater circuit dont start working and getting a reading until it warms up? Is this why it keeps throwing a P0135 trouble code?

[@michaelgalvin1024]

Hi Paul Nice one, your keeping it tight. Do you intend sharing those work sheets with the premium subscribers? Thanks for the great classes, Mike from down under

[@markchidester6239]

who were the morons that put a thumbs down to this? Awesome info! Thanks Danner

[@ScannerDanner]

Thanks man

[@TheCoatneyadkins]

prolly folks who don't quite understand the info...I know I had to go back and brush up on my basic electrical a bit before I could understand certain things in certain videos.

[@sinegra30]

Scotty Kilmer through his 7 fake accounts?

[@IsshmanGarcia]

Nice Follow up!

[@ScannerDanner]

Thank you

[@neryenri6567]

HI, there I have a 2012 honda accord 2.4 code p0135. O2 heated circuit malfunction. Intermittent problem . Replaced o2 sensor oem. Checked resistance on circuit from ecm to sub relay and from the relay to sensor . All within spec. The ecm it is shutting down the driver ground signal. I replaced ecm vehicle was driven 300 miles and set the same code p0135 again. Any feedback on a problem like this that you have experienced??

[@Dexron3]

Hey Paul great vid!. Question: Would the worksheets be added to the ebook for currennt owners?

[@ScannerDanner]

It will be probably a year before they are done and it will be in the form of a workbook. I don't know if I'll make it available as an eBook or not yet. Thanks!

[@jasonc.4683]

Hey professors just stopping again to see some material to refresh my mind and man it's like I learn something new everytime. But I can't wait for that notebook with the questions and answers or workbook. That video u just released on the can questions on ur premium channel is freaking awesome. If the workbook is like that holy crap that will be awesome follow up material. No rush professor but u got alot of eager fans out here. Thank u god bless

[@bradjim8355]

What would cause a vehicle to stay in open loop? My 92 explorer is running very lean and never goes into closed loop, even at 180 degrees coolant.

[@ScannerDanner]

Bad O2, signal wire of the O2 shorted to ground. Vacuum leak, low fuel pressure, restricted injectors, bad map or maf sensors etc etc

[@themusiclab2621]

I have a question ,my 05 toyota 4runner has a p0420 the truck is running perfect but is burning more fuel than normal i can tell,b1s2 is mirroring b1s1 is that mean i need a cat? there's all kinds of information out there,it doesn't really feel like the cat i clogged what should i do? Thanks

[@IamReadyToRock]

[@hole1stdrillpresschannel]

Very interesting! Thanx man!

[@likezdislike]

does this mean bias voltage and reference voltage are the same?

[@ScannerDanner]

no sir, but some will use the wrong term when referring to these, myself included lol

[@likezdislike]

@@ScannerDanner Im confuse because I want to know what is the difference between bias and reference voltage

[@joachimjohan1215]

Would a power probe hook voltage ref mode 1v power be 100% safe? maybe in series of a normal test light ???

[@ScannerDanner]

I'm sure it would be

[@joebrian2176]

@@ScannerDanner Am joseph from Ghana 🇬🇭 am having difficulties in subscribing please Dan ĺing me up to your Classes

[@ScannerDanner]

@@joebrian2176 email this message to [e-mail] and we'll see what we can do to help

[@KFCMasa]

brand or the name of the scope please

[@joshymathew876]

Hai SD, my 2008 GMC Denali is throwing P1133( heated oxygen sensor, insufficient switching bank 1 sensor 1) P1153( heated oxygen sensor, insufficient switching bank 2 sensor 1). Changed the oxygen sensors and again the same code is coming back. Any suggestions? Thanks

[@ScannerDanner]

Check your heater circuit for those O2 sensors next, then make sure you have no exhaust leaks

[@Thefox2000unit]

At around 38 mins, if the 5v signal circuit is open how would the pcm send 5v? The return part of the circuit for the 5v is open so there shouldn't be 5v. What am I not understanding?

[@ScannerDanner]

I'm not sure what your question is, sorry. The PCM is sending a weak 5v bias voltage down the signal wire of the O2. I thought this video explained that very well. I even showed it being pulled to ground through my body.

[@ScannerDanner]

Sorry man, wrong video, thought you were talking about this one kzbin.info/www/bejne/rGm7o4BjbKeohck Watch this one, it will help. Let me know

[@markela1313]

got a question 2006 Kia sorento 3.5 v6car came in from some one p0134 p0154 new ntk sensors some one changed got B+ ground signal sensors r active when at 3000rpm or higher checked need some help finding the problem

[@ScannerDanner]

It is becoming more and more difficult to answer questions here. I have 80,000 people asking me for help now. So I have created a forum to help you guys better. It is free to join and we can exchange pictures, wiring diagrams and waveforms if needed to help guide you through the process of troubleshooting your vehicle. Thank you so much! Hope to see you there. Paul Danner (ScannerDanner) www.scannerdanner.com/forum/post-your-repair-questions-here.html

[@jasdeephari1]

HI PAUL MY CAR LED HEADLIGHTS FLICKER WHEN ENGINE RUNNING WITH ENGINE OFF ITS WORKING OK ANY IDEA WHAT IT COULD BE .

[@ScannerDanner]

Check your alternator diodes. Perform an AC "ripple"test. Use a digital multimeter set on an AC voltage scale. Connect red lead to the alternator battery post and black lead to battery ground. Engine running, max allowable is 300 mv

[@jasdeephari1]

THANKS WILL CHECK THAT .

[@leebarnes655]

Fault should be with alternator brushes worn to marginal length making intermittent contact. Diodes usually don't fail in flicker mode. Be sure to load the system with headlights on while engine running too, but Paul's test method does have some merit to see the issue. Misapplied AC voltage scale takes advantage of the tool at hand, but pretty sure that the typical DVM will not be fast enough to capture the signal at the readout - a scope sure would do it though.

[@mustafa2mahdi240]

very good vids . I want to wach your other channel is it available for Iraq ??

[@ScannerDanner]

It is now my friend. Go here to subscribe www.scannerdanner.com/join-scannerdanner-premium.html Thank you so much!

[@joachimjohan1215]

20:00 minutes

[@HollywoodRoseJack]

Paul, is the book different from the one I bought from you, Engine Performance Diagnsotics? Because pages don't match nor have the same content.

[@ScannerDanner]

Same book, same pages. Do you have the binder version or the spiral bound version. They are both the same but the spiral bound version has two slides to one page. So for example, I am on Chapter 5 (Section 5) page 12. This would be Chapter 5 page 6 (5-6). Everything is split in half because of two slides on one page. Make sense?

[@HollywoodRoseJack]

I have the spiral bound version.

[@ScannerDanner]

So if you see me on chapter 5, page 12. It is still labeled as page 12 but it is on 5-6. Turn to it now, you will see what I mean. Putting two slide on each page save half the weight in cost of paper and makes it less expensive to ship for you guys.

[@HollywoodRoseJack]

Got it.

[@ScannerDanner]

Sorry for the confusion and thanks again!

[@billrimmer5596]

Liked how your body pulled it down. Lick your fingers and it will go down a lot more. Right? Much less resistance. Starting to understand the buffer on the vantage pro. Would help to c u concentrate on that one feature. Like does it start automatically every time u start testing? How do u make sure your not looking at buffer instead of live? So far that has been the most difficult part of the scope for me.

[@ScannerDanner]

Good suggestion! Thanks Bill

[@jdean399]

Paul has a very good series on the verus and vantage pro on his other channel

[@TheCoatneyadkins]

pay attention to his students talking talking right before 28:00 min. .... teacher: Shane brought one in today with a 420 code. student 1: I hope so... student 2: yeeeeaaa .... LMAO wonder if he caught that and left it in anyway...a little Easter egg for the astute viewer! lol

[@ScannerDanner]

haha I did and get these kind of smart ass remarks all the time. I don't mind though

[@TheCoatneyadkins]

ScannerDanner all jokes aside though this channel is a diamond in a mountain full of coal!

[@ScannerDanner]

Thanks brother

[@Mechanicsville804]

Thank you! John 3:3 Jesus answered and said unto him, Verily, verily, I say unto thee, Except a man be born again, he cannot see the kingdom of God.

[@tenzackyogi1742]

Its BIOS.

[@prinsafro2148]

hi paul i wont your books ware i fwond????

[@ScannerDanner]

www.scannerdanner.com Thank you!

[@vicferrarisgarage]

Do you teach not touching your vm leads when reading voltage. Human body salt/water will give false or misleading readings.

[@ScannerDanner]

Only when performing a short to ground test (ohmmeter) or when measuring certain high ohm circuits with an ohmmeter. Other than that, touch away 😉