how to read 02 sensors, short and long term fuel trims 

Very educational.. I'm a diy person and bought a Zurich z8.. now I understand these readings better.

Incredibly informative material here, brother! First-class all the way! I have been watching videos and clips trying to learn how to read live data for 20+ years still not quite understanding it all. In 14 min you just topped all of the others! Wow! Thank you sir. Outstanding!

Learning to read my scanner and was wondering what some of the terms and readings were all about, and wow, I found your very informative comments

It’s very good explanation video, Make me more understanding about the STFT and LTFT Thank you

i'm starting to understand this whole thing.Thanks man

The point you made about the cold air is true. If you change the air fuel ratio outside of factory you'll need a tune.

I had the phone plugged into the truck stereo not as noticeable through the phone and laptop. Another good video.

You do well on explaining as well diagnosis Knowledge is great for self taught good job

Your doing a good job keeping us informed thank you

One hell of an informative video.

Awesome video! I’ve had a scanner for a while but never understood what exactly to look for as far as live data in diagnosing my problem. Thank you for your time!

2016 Sonata Hybrid 151k miles Idling in Maint mode after 20 mile drive Smooth idle No power loss No mpg loss No rotten egg smell Some lifter noise at slow speed, light accelerator, uphill before gearing down. P0420 New 02 sensor on Bank1 S1 (cat is in manifold) Sensor 2 (in front of lower cat) is factory. Any ideas would be greatly appreciated. 👍 STFT 15.6% LTFT -32.0 02S12 (V) = .790 V 02S11 (mA) 0 to -.05 STSO2FT1 -1.6% LGSO2FT1 3.1% CATTEMP11 (576 Celsius) CATTEMP12 (400 Celsius) LAMBDA11 0.998 ish LAMBDA 0.999 ish

2001 Toyota Camry 2.2 le , o2 b1s1>>>> 3.25. +/ - 02b1s2>>>>0.050. What is o2b1s1 reading mean ? Your video is very very informative thanks

13:00 STFT POSITIVE adding fuel ~>Vacuum leaks STFT NEGATIVE taking fuel away ~>Fuel system issues (injectors or fuel pressure regulator) Correct???

Best video.was waiting for the live data on the trims wave forms

Easily the best video on o2s and trim I've seen. No BS Straight up knowledge. Excellent video. Thank you

Exactly now IM a mechanic cause of trying . If you don’t try you never know

Fuel trims somtimes are not accurate, caused by one the sensors, like mine the MAP sensor cause both fuel trim to be at 12 to 14 percent, i tought i have vacuum leak, but it was the aftemarket delphi MAP senosr reporting wrong values to the ECM, i just put back the OEM sensor and the fuel trim went down to 5 percent. I couldnt believe it, the initiale issue was rought idling and somtimes engine misfire, but it was the ignition electric connection wires were loose at the aftermarket start button system, basically i create the problem overtime by using bad quickdisconnect connector, i replace the connector and problem solved partially rought idle and misfire, but fuel trim problem got fixed by installing OEM MAP sensor back.

I have a 2014 Jeep JK that has had a small engine surge while going down road. At idle, not detected. Least surge is not detected on tach, the up/down is so quick, really doesn’t have time to register. Worst cases, while going up a hill around 35-40mph, by ear it is swinging much more and you can see on tach that it is 50-75 rpm fluctuations. No codes at all. Looking at o2 sensors and fuel trims after engine is in op temp but at idle, o2 upstreams are bouncing all over 75mv up to 800+. Again it is so quick, can not grab a solid number. Downstream sensors however, b1s2 sits around 250mv while b2s2 is around 685mv. While these o2 readings are taking place, fuel trims stftb1, stftb2 and ltftb2 are bouncing between .0 and -3.9. Ltftb1 sits at 0, no movement. It will change when revved up, but still not hanging near where the others are going. Could b1s2 o2 sensor be going out? Could that cause my surge? Shops I have taken it to say no code, no problem without looking at it to see what I’m hearing and seeing. 84k miles on engine and first issues I’ve had. Owned since new.

Thank you for teaching me how to read my sensors, you are a life saver. Awesome video.

9.4 fuel trim is a bit high.. 😅 I won't even tell you what mine was then lol I haven't got to figure out my p0171 lean code yet but I think it was because I didn't have an air filter on my cold air because it fit different on my 98 cobra, or i need to plumb the valve cover vent back into the crankcase for positive vacuum because the 98 was a little different that the 01 cobra but it was dumping about 25% on the trim. Luckily im still breaking in the motor so there was no getting in it with those trim levels.

This is a very informative video

I was looking at the reading on mine 02 sensor it's not responding and it's stuck on a number I looked at the graph flat line is that a bad O2 sensor it's causing backfires and a random misfire

Hey. Superb video. I have strange problem with short fuel trims. My engine is BMW M54B30. On bank 1 i got +25-28%, but on bank 2 it is ok 0 to 5%. I know that my oxygen sensor after cat on bank1 is dead. Is this can affect on fuel trims? MAF is working, I checked rubber hoses and there is no cracks. Help please. Thanks.

Hello I have a 07 g35x and my long term ban 2 is staying at 35.2 everything else is fine do can you tell me why that’s happening is it a oxygen sensor and how do I figure out which sensor it is I’m also get a code p0174 I’d appreciate your help

Got P0171 lean bank 1 on 03 S10 2.2 engine , LTFT at 1100 rpm 21.9. STFT 3.1. No vacuum leaks , would you have any ideas ? Thanks , I have 18lbs of vacuum at idle

On a cold start, does the oxygen sensor post cat heater command need to be at 100% or its okay to have a a 10% value ?

Exelent explanation on how this o2 sensors work. It might take me 20 times to see this video but you went really well.. Thank you 👍🏻

Great video I have a 1997 suburban 454 3out if the 4 o2s are reading 700ish MV and long term fuel both banks is +9 do you think my o2s are bad? ThNk you for any advice...

Greetings, I have a suzuki Kizashi 2.4L S. The ecu throws check engine light with p0101 code. The fault code is thrown under 3 conditions: 1. Coasting downhill with zero to minimim accelerator input. (Tps at 19.6 degree, MAF at 10-11g/sec) 2. Cold start after 24+hours in colder environment. Ltft drops down suddenly to -11 to -17% but goes back to 0-3% 3. High rpm idle test. Rpm set at 2.5k, stft increases from +1% to 5% and then returns back to 0%to1%. Can you suggest a way forward? I also have a bad valve cover gasket

I have 1500cc petrol engine in toyota ...... I tried two maf sensor one giving 1.3 g/s at 650 rpm.... Another giving 1.7 g/s at 650 rpm.... Which one should i use for better fuel economy.....plz reply

This is an incredible video !!! Amazing explanation on live data

Hi how are things ? I have a 2011 Mazdaspeed 3 2.3L Turbocharged with Rich's issues I have the long term fuel trim at sometimes -16, -19,- 17, as the car warms up it becomes more negative, speeding up the long term fuel trim fuel trims, it goes down to -9.50 or sometimes -10.50 could the problem be a vacuum leak, or air leak after the MAF sensor? the short terms always go 0 -0 sometimes +7 but when accelerating sharply sometimes it jumps to crazy numbers like -17 or sometimes +20 what could be the problem friend? I would like to hear the comment

I have a 2004 liberty 3.7 I got two codes, p0132 and p0152 every thing from the pcm to the connectors is okay, I checked resistance in every cable and all are okay, I changed both o2 upstream sensors oem, and still the same keep steady Reading of 1.270 on both o2 Sensors, down stream sensors Reading are weird also, I got 0.035 on both sides sometimes they go up to 0.700 and sometimes the upstreams start to oscilate but for a few seconds. Do you know what can be causing this?

Hi, I hope you’re still checking your channel. I have a question on data stream codes. What does it mean when my oxygen sensor codes give me N/A instead of a number. (O2B1S1 N/A) I have a reading for B1S2 but then not B2S1, B2S2, B3S2, B4S1 (all have N/A). BTW thank you for these videos. Could you do more on all these other codes? SPARKADV, MAF, etc

I use obd2 on my toyota vios 2004. The o2 sensor is one "Percent" not "volt". Please help.. is there nornal percentage for o2 sensor? Thank you.

Thanks for the information, I'm no mechanic, trying to fix an Issue I'm having with my Acura TSX 2009, it's giving me error code P0131, changed the spark-plugs, ignition. coils and even fuel injectors, but problem didn't go away. Car doesn't go over 20 mph ad checkengine is blinking. I got Foxwell scanner recently, but not sure what numbers I should be looking for when in comes to O2! SHRTFT1: -31.3, LONGFT1: -3.9, SHRTFTB1S2: -31:3

got a 09 qx56 infinity, longft1 -3.9 shortft1 -3.9 longft2 -7.0 shorth ft2 3.1 02B1S1 2.47 02B3S1 2.255 02B3S2 0.080 02B1S2 0.050, getting p 0420 code, change bank1 sensor 2 and MAF sensor, CEL stayed off for a day and back on now. took off exhaust bolts and was told CAT looks fine, any advise.

what does it mean if both my o2b1s1 and o2b1s2 go to a steady 0.20 (could be 0.020 i forget, but point is it's steady and will have pending code) when the fan or stereo is on? when i turn both off, those sensors seem to fluctuate again. also, are the o2 sensors supposed to go to steady value like i mentioned in park? all my o2 sensors (2 banks 2 sensors each) drop to a steady 0.20 or 0.40 in park. or is that a function of not being in closed loop like you mentioned, because i didnt let my bank 1 sensors run long enough (because of the stereo or fan being on)?

hi does anyone know what it means if i have a stft b1 s2 (%) NA and a stft b2 s2 (%) NA ? Hope someone can clarify this for me thanks.

hello. SHRTFT1(%) = +6.3 and LONGFT1(%) = -7.0 , is good or bad? Another question: SHRTFTB1S1(%) = 2.3 and SHRTFTB1S2(%) = -100.0, s good or bad?

Great video's on live data. I'm new to reading live data and I need some guidance on how to diagnose a high-idle condition on a 2005 Corolla. Idle is around 1,000 RPM and is a quite rough so I assumed a vacuum leak, but I've checked/changed all vacuum hoses and even replaced the MAF sensor and confirmed no manifold or PCV leaks. Since the car is 18 years old (original owner), I've replaced both O2 sensors and all injectors which improved the vibration level, but it is still present. The last thing I did to the car was to clean out the throttle body (there is no IAC valve). Here are some live-date anomalies (at operating temp) after my last repair: SHRTFT = -20.3% (LONG is 5.5%), TP = 14.9% and will not go to zero even though the adjustment is full minimum, O2S11 = 2.914V (S12 is .095V). Do you have any idea what may be causing the rough, high idle?

Thanks for the video. I ran the OBD on my car, monitored values real time and found that my bank 1 sensor 1 and bank 2, sensor 1 are showing values between 4% and -4%. However, bank 1 sensor 2 and bank 2 sensor 2 are both stuck at 99.22%. Getting P2096 code after I got the shop to install the complete catback solo exhaust. What's your take on this? Can't be the sensors going bad. I am assuming they didnt plug it in properly etc....

Thanks for making this video. It helps me a lot. What numbers patterns indicate O2 sensor is bad? Like, number not moving like your sensor 2?

Very nice video good info. I'm sitting at idle and it's all negative for stft 25 and ltft 35.2. 2014 gmc sierra but I get a code saying it's to rich on bank 2. Any suggestions

Thank you sir. I am having about 28 positive at longtrim. I will check for a air leaking somewhere .

I have a 2001 chevy prizm 1.8 toyota vvt , (no i or 4 , different engines). Should the readings be the same where the O2 sensors or air/ fuel sensor and fuel trim readings are concerned? Thanks. J.

Should I be checking theses while idling? My truck seems to be having issues when I am towing and going up hill. No codes, no misfires, took to shop for a trans flush. Dropped pan, all looked good. No metal in pan and fluid wasn’t that dirty. When I punch it, I can feel and hear that my truck is not shifting like it used to, and when I am towing up hill my truck will jump when I’m 1st or 2nd. Once I get pass 2Nd truck seems to run fine. So I have a OBD reader plugged in right now and I am trying to understand the terminology etc. so, when checking my O2 sensors and fuel trim, should I be checking while driving or in idle? Bc when I step on it, my % goes well over 10%. Hope all this makes sense. Thanks for your vids

It sounds like you are saying the cold air intake, bigger intake air hose, or bigger throttle body does not make a difference since the ECU will simply adjust (eg keep the throttle body more closed) to compensate/restrict the extra air intake to keep the same 14.7:1 air to fuel ratio. Correct?

Nice video, I am wondering, what about bk2sn2? I just don't is it.

Excellent Video... much appreciated. I have a 1996 E-150 5.8L EFi . Have ABS light on, OBD2 reader says "This vehicle does not support ABS communication" is that correct ? if so do you know of any other way to identify the faulty sensor (assuming it is a sensor fault) also..... when backing off the throttle the RPM holds, at whatever RPM you were at, for 2 - 3 seconds before dropping.... any ideas ? there is the occasional hickup at idle and sometime it stalls. PCV valve replaced. Any help would be much appreciated. Regards Paul

The B1S1 and B2S1 sensors on my 2013 jx35 are reading 1.9-2.2v at idle and go up to 4v while coasting. Is that bad?

Hi, one of my upstream sensors on my 2014 Ford Mustang is showing a negative value. My STFT for bank 1 is +34 and for bank 2 it's -25. Both long-term are 0. My vehicle is not running well. Rough idle, poor acceleration, bad gas mileage, sometime I smell the rotten egg/sulpher smell, etc. No check engine light. Please help. Thank you.

Hi, my O2 value Is at 0.75, and does not increase or decrease when car is revved, does this mean my O2 sensor is faulty ?

These values while the car is not moving, idle, what happens when you step on the gas or open the throttle? How much should the short and long fule trim be???

Cold air intake will gain power. A lot of factory ecu are calibrated to be a little richer at wide open throttle, adding the cold air intake leans it out a little and gain power. Closed loop is only used during idle and cruising.

So the SHRTFT B2S1 at -1.6% is normal?

Great video. I have a vehicle that reads: O2 B1S1 .9mv O2 B1S2 .0mv O2 B2S1 .0mv O2 B2S2 1.0mv STFT bank 1 -20% STFT bank 2 30% LTFT bank 1 -4% LTFT bank 2 30% Inj. duty bank 1 4.4msec Inj. duty bank 2 11.5msec

Thx buddy for this information

Awesome, was looking at the live data the other day for a p0141 on a rav4, and you are correct not a lot of good content exists, so thank you and keep'em coming:)

Got negative ten long term fuel trims a touch higher on bank 1...a bit low o2 sensor readings on upstream...Maf reading at about 4.3...2001 nissan sentra gxe with the 1.8...runs pretty good but a little rough on the idle...cleaned throttle body and iac...experimented with the egr...any ideas?

Just subscribed. Would be nice to see examples of what your explaining.

Thanks, watched video twice. So understand how its all goes together. ? My shortT reading -17. Longt 0.0 so how I'm understanding my issue is not vacuum leaks. Itd a fuel issue. . so my ? Is I have been putting fuel injector cleaner and its not that. So I'm gonna go with a fuel injector is clogged ? So I would have to basically clean all of them because I don't know what fuel injector is they don't label which one would be the one bad right? Thank you so much for your help. I so understand how it works. So what would I do next do I put maybe a direct cleaner to the fuel injectors or do I have to clean each one by hand which I don't even know how to do I'm going to touch them before and I'm a female mechanic for 25 yes. You and wiring electrical was not my thing though I so confused with injectors does this but if you could like give me a little push or something what should I look for I mean what should I do for the injectors and if it doesn't clear up see my fuel pump was a new fuel pump was put in like I want to say maybe a year and a half ago. I'm leaning more towards of fuel injector clogged I think thank you again have a great night

thank you for your information. l really appreciate it!!!!!!!!

Love the explanation. My Camry stft 0.0. And ltft 38.9. I change maf and 02 sensors also done smoke test

My short term fuel trim (B1-S3) is reading 99.2% with no fluctuation, is that good or bad ? It's a 99 Blazer 4.3L and B1-S3 is the last sensor. I have B1-S1 driver side. B2-S1 B2-S2 B2-S3 is on passenger side.

I have a 2000 Ford expedition 5.4 my bank 1 is reading -22.7 bank 2 reading -2.3 both first o2 sensor reading good .075, both second o2 sensors reading 0. Do I have multiple issues going on.

Excellent video. Thank you.

Thanks bro fully understood

How do the first 2 Pids here help in diagnostics, I've been told to ignore them, especially if they are at 99%.

What if you drive a Ford and no O2 sensor voltage can be displayed? My bi directional tool can only display microamps on the downstream sensor, which is meaningless to me. I CAN see voltage on my GM and Chrysler vehicles. Does Ford use a different data point at the ECU to adjust fueling?

My 02 sensor reading is negative 8.6 shortFT and negative 7.0 LongFT . Is my upstrean and downstream 02 sensor is bad ? There's no code . My engine stall every after start like its too lean and no air coming in to combustion. After stall its running fine . Fuel and vacuum is fine .

I have a scanner reading on the sensor called Lambda Correction, and it shows a value between 3.5 and 5.0. Is this the same as STFT?

Great explanation. I have a Toyota Camry 2.5l Stft. 0.08 and ltft 39.8. I smoked test and did not find any leak. I changed plug coil pak injectors 02 sensors and maf. Still getting low mileage. Pl help 🙏

What if your neg. on the short and long term fuel trim? GM 2.4 2000 Grand Am. Thanks in advance.

Hi, I'm having an issue with my car idling kinda rough and hesitating especially when pulling away from a stop. I'm kinda new to using live data I just wondered if you have any suggestions what I should be looking for? thanks, cars not throwing any codes so I'm kinda struggling with where to start.

I changed my plugs, ignition coils and fuel injectors on my ford e-350 6.8 v-10 because I was getting engine miss fire codes and I kept getting the codes after I changed the plugs, so I went ahead and changed the coils and injectors. That solved the miss fires but now it won't pass smog and the other day I noticed I got a rich fuel code on bank 2. The upstream o2 sensor voltage fluctuates between .100-.800 volts on the bank 2 side of the exhaust but the o2 sensor voltage on the bank 1 side stays steady at around .900. which. My question is which o2 sensor is working properly the one staying at a steady voltage or the one that's fluctuating?

My o2B1S2 V read 1.0 continuously, fuel system 2 also says nothing instead of OL or CL it’s just a ? Mark. Not sure what that implies, Used the same tool in video thanks

Why is the b1s2 showing really low voltage? I have this on my car, the b1s1 is fluctuating like normal, but the b1s2 shows between about .050 and .075 Thanks!

Thank you for the information, I have a Toyota corolla LE 2012 and I failed the smog test because of 02 sensor and cat but my car did not show any code also I follow a Toyota drive cycle and I drove 360miles highway 55 t0 60 after I slow down without using break just helping the car with hand break to 35-45 but still not ready! but when I plugged my OBD2 IT SHOW THAT MY O2S1 bank1 (V)=3.306 AND O2S1BANK2 (V)= 0.660 the car was warmed up for more than 10 min ! please do I need to change both 02 and after drive it probably it will make the car ready for emission! thank you very much

I changed an exhaust manifold ,after market, and then the oxygen sensor stayed at .999 and now changing

Thanks for the great video. Helped a lot. I have a problem you didn't cover hoping you could answer for me. My STFT B1 S2 is 99.2 and my STFT B1S1 is - 63. If you could tell me what that is. And what's causing the 99.2. It never changes it like it is stuck. Thanks

BANK 2 for me is ~50% STFT! and high LTFT also. I used a smoke machine and found a few intake air vacuum leaks.... but still remained. I used the smoke machine into the TAILPIPE and found a badly leaking exhaust DONUT from the exhaust manifold. $5 fix... will find out tmrw hopefully!

What if my Longft1 and longft2 are the ones that are close to 0?

I have p0430 on my Lexus gs300 any advice please thx in advance

Bro.. I and dealing with 2005 toyota seinna.. Got a code p0174.. But custormer wanted further job like valve cover gasket, rack & pinion.. So code got cleared and i was trying to see if tht code comes back.. It haven't yet but problem i see is bank 2 seems running soo lean since long term is around 19 and short term is like 3.. Bank 1 seems ok adjust its self... While looking at 02 reading upstream is giving 3.3 v which seems coming from pcm reading.. But down stream showing like .05 like in ur video.. I am confesed here...

On my 2003 escape all starts with P2197 then cylinder 4&6 misfire :( Find no leaks, cleaned sensors , changed injectors etc. O my both LONG reads are at = 0 FUEL = CL FAULT ECT = 76 SPARK ADV = 7-12

Hey there question, so in the same way learned by doing the work myself cause I couldn't pay someone but I'm lost when it's coming to this 02 to short term trim stuff. I have a shrtftb2s2(%) 99.2 and my longft are at 25. I have replaced my intake gasket and put old but good I believe 02 sensors in and it shows my 02 sensors are working and shrtft are working fine. Where should I go from here? 01 Silverado. Truck runs bad in open loop then better in closed loop but still not like it should. Any help would be great.

Any ideas as to why at idle, MAF at times goes below 2.0 g/s and Oxygen Sensor Current (B1-S1) goes into the negative? I have 3rd GEN MINI COOPER S

My long fuel trim is at 24.0 and my short fuel trim is at 0.0 what that mean??

If O2B1S1(V) reading just only stays on negative, which parts is abnormal? Mazda 3

Real good explanation of FT.

Dear sir , i have some kind of these issue in my car bmw E46 and it says voltage failure bother oxygène sensor ( v ... Fail ) B1S1 AND B1S2 . Sir i have changer the oxygen sensor and still same fault code 2C45 DME : oxygen sensor before cat. Conv.1. sir plz if you could help me to solve this problem . Thanking you in avance sir . Best regards.

Hey great video but I got a question that will stump you.2001 mustang v6 305k miles cats went out .I replaced the factory cats with flowmaster universal and made basically a entire pipe and 2 new downstream o2 sensors.but at idle my b1s2 reads .060 on average b2s2 is at the same but will go up and fluctuate a few times and back down to around .060...do you tft think I may just have the wrong or defective o2 sensors .Car runs great no power loss or smoke.front o2 sensors read like they should .hasn't thrown any codes but won't complete catalysts monitor.

Very useful brother. I'm working in NISSAN dealer in Dubai. It's much helpful for me.

How did you see soapy bubbles from outside of a vacuum?

Need help both SHRTFTB1S2 & B2S2 ARE READING 99.2. While the front 2 o2 sensor are reading 0.0 to -4.6% Any ideas ( GM,03 5.3L

Thank You!! Very informative video.. but what about diagnosing faulty OSS or (Output Speed Sensor) on Transmission 4.6L? I've already wasted money replacing it with 3 different ones.. still having code, and engine light, and O/D light blinking!! Wires all seem to look fine.

SHRTFTB2S2 99.2% what’s that? I have code P0440

When I look at my o2 sensor graph my b1s1 shows .00 to .01 volts and the same with b1b2. When I give it gas the volts increase. Are these bad sensors?