I learnt the fuel trims lessons (2 parts) from this guy, everything he says, guys. Super useful, accurate.

Didn’t hesitate and watched those 2 videos. No regrets, every second was worth it, every second full of useful information.

You are such a nice person making us all so comfortable attending the free tutorial. The knowledge that i learned in just the last few hours benefited me my whole life.

You’re doing great work in your channel. I have recently subscribed and I like all the information that you share. Knowing how and why things work has to be the most appreciated part about your videos. Great work!

Great job on your videos. I have had a auto shop for over 31 years and I am using you videos to train my techs.... keep them coming!!!!

I wish everyone explains the way you do ...amazing !! Keep up the great job

Thank you for putting all of these types of videos together. Very informative!

I was a fire service instructor for many years, a SME for the FBI. Nice work here. You ascribe to my favorite training phrase; "Tell me and I understand, show me and I learn."

So I came across your channel while studying for my ASE recertification test. I love what you are doing any you explian everything very well. I have been a tech for 15 years and I can honestly say you have a better understanding of Automotive technology then most of the technicians I have worked with.

Excellent intro to the basics of diagnostics. Thanks for sharing.

As a long time subscriber of both of your channels, I owe you a HUGE!! thankyou. Your videos along with your unique and specialized brainstorming super powers, have pushed me from a basic DIY mechanic to a auto technician. Your methods of diagnostics, along with the WHITE BORD OF KNOWLEDGE are truly amazing. I have been working at a shop for 3 months, and have even received a raise today because the owner is so impressed of my ("your") scientific methodology in diagnostics. YOUR strategic diagnostic mindset and teaching skills has allowed me to be more than successful. I know 30+ year techs could learn from you. You have given me a career from a Hobbie. You are 100% responsible for my success. I truly am great full. Please keep sharing your "brain". Sincerely Jay

Great information on the air/fuel sensor. I really enjoy your video's. The information is awesome. Thanks for taking the time to put this on!

That's Mr. Asshat to you! Don't know how I missed this one earlier. Thanks Matt.

Your bookshelf looks a lot like mine. Nothing better than knowing how to do your own work. Another great and informative video to po it into the knowledge base.

For me, your board truly is "The dry erase board of Knowledge" Thanks!

Well done, well spoken and understood , great info Matt Thanks.

This dude level of teching is high.. I dont have to repeat his videos to understand👍

The best tutorial I have seen online about wide band O2s. Thanks So Much!!!

You are great at teaching. For a long time I’ve had a lean code on my F-150 2001 that I could not understand even after getting a BlueDriver scanner. I’m so happy I came across some of your videos. I get now. Thank you..

Thanks for your informative video. I recently swapped engines on my 97 Camry 2.2 and immediately got a CEL for IAC P0505. Turns out the engine installed is a Federal and previous engine was California emission. Replaced with a Federal ECM and the CEL P0135 came on after a 5 mile test run. Next step to take is replace my California fuel sensor to Federal standard oxygen sensor. Pending change out, will post with results.

Great video amigo! I'm learning about these in auto class right now and I'm a big fan of the latest technology. Thanks for the tip about the manufacture specific service manuals.

Actually, your videos are very interesting and not boring at all. I would love to come to your shop and actually sit in for a lesson or 2. Awesome work!! So clear. Thank you.

Thanks sir appreciate your efforts.I am from Kuwait and i always watch your videos .

I'm from Oman,, 10 years since this lecture was given by Matt and I'm still referring to it until now. Very scientific and rational speaking. Thank you Matt.

There was one time I was looking at video about MAF and IAT functionality in a car. I saw a video from the suggested list titled how engines work. I clicked on it, I didn't finish the video because I had to go to a family gathering however when I came back I couldn't find your videos anymore and tried so hard until I finally came across to your video and subscribed. I have not watched all of you videos yet, but I'm really interested because of the way you explain real life problems that we encounter and how to properly diagnose and eliminate probably causes until the final solution is found. Thank you and keep up the good work.

Good stuff, easy to understand. Many thanks.

You are so humble and I think you must be a Baha'i to be so good at your training. Thank you.

Thank you for time spent. Appreciated, I’ll get this figured out yet. I bought a mid range scan tool $500usd . No regrets, I just have to learn what to look for. Bought it to help me with bank 2 s2 after replacing sensor, began throwing new codes. Stuck lean low voltage. Cleaned and switched sensors and the old one is at least modulating. Time will tell

Stoichiometry that was a new word for me. I looked it up to grasp it. What I interpreted. It is looking at the differences above and below baseline. Using those values to come up with a diagnostic picture.Am I looking at that right.I get what you are explaining. Very well in fact nice job. Just the vocabulary was getting me.

Greetings sir. I would like to thank you and commend you for the great work you do. the way you present the content makes it very easy to understand concepts that were difficult for me in school. Be blessed and all the best in all your work.

Great video... I'm learning a lot... Thanks

Great information and very educational! I am glad I discovered your video. I have subscribed to your channel. I look forward to watching more.

So after my last comment of your video, and subscribing, I was pleasantly amazed that you had many many videos on auto repair! So I have been watching them religiously, and I feel like I am becoming more and more like a mechanic. What I am trying to say is that when I go in to see an auto tech about a problem, the fact that I can explain what I am experiencing in auto jargon, and when I go in to pay the bill, the tech can explain to me what he found and I freaking understand what he is saying! It is so F%$#%$# awesome that I no longer experience anxiety, I don't start hyperventilating, etc. Anyways, you sir are an amazing teacher, and if you ever offered courses that I could take locally, I would find a way to go to them, even if I had to sell my wife, and the things that I loved. Thank you!! PS Don't worry, I already got rid of my wife a long time ago. :)

thanks a lot I really learned a lot from you. thank you hope you continue making helpful videos like this .

Great information in this video. The real nitty-gritty starts at 7:33. I watched both Part 1 and Part 2. Kinda long, but well explained and with real-time graphs.

It ended on a cliffhanger! I learned so much from this video, thanks for sharing. I've been pulling my hair out diagnosing a P0420 code on my toyota and I was thinking the O2 sensor was bad but turns out its not even an O2 sensor at all.

I'll bet that as soon as you get the wide-band understanding by heart, they'll bring out something new and you'll be learning all over again.

Thanks for the training and for using a subaru. I have a 2016 Subaru WRX which I think, reports the equivelance ratio as Lamda. I get very close to the same waveforms on my scan tool as you got on yours. Once again thanks for the training.

Brow, I like the way you structure your thoughts. It helps a lot buddy. Congratulations on this awesome content, and thanks for sharing with us! As you, I also like to understand all the details of everything...LOL

Thank you for this video, i hv learned heaps and it's actually helping in my diagnosis👊. Can u plz add Understanding of CAN BUS and diagnosis...?

Good stuff man thanks for sharing and keep up the great work!

This video was very helpful

Matt, Was just going through some of your older vids. Dude your humor is a class act. In this vid, you came out strong. Within the first minute, you say some of the people on the internet couldn't diagnose a diaper rash let alone a problem on a car. Or them people on the chat rooms couldn't fix a sandwich let alone a car! It is as funny as the first time I hear it. Besides the high quality train of thought, I know why I keep following! You are one twisted fella! LOL !

Good stuff Matt...

Great info, Thanks

Matt good job bro again

thank you so much for all u had done

Hey Matt..Im just commenting at about 3 minutes in to say thanks for the soda but I just opened a cold beer and am relaxing and looking forward to the rest of the vid. lol.

great class.watched it twice..

I am thankful to you.

You are the best.

you are the best!!!

Hi Mat I have watched every single video of yours and never got bored, In fact they are very educational and interesting. I have done my HND on automotive engineering. By watching your channel In past 2 months I have learnt way way more than what I learnt during the 2 yrs of the HND course. I really loved watching fuel trim videos. I hope you upload more videos of customers cars that has some kind of fault in it which was never fixed by the corner garages especially like the one that had exhaust restriction. Did she get really happy when you fixed the problem for her? Thanks

ey bro. I came to youtube seeking copper and found this gold. good job

I love your class

the torque vectoring system would be neat to learn about and work on

thanks.....very good---hope the cheap harbor freight scanners will work on this by the time I have one to work on....thanks again...bob

Really good video. Your voice and the way you talk reminds me of Jello Biafra when he speaks.

this video is very interesting!

THANK YOU FOR HELP

Fantastic looking to test my afr on a 07 Honda CR-V 👍

Love the videos. Thanks. Just a bit of info. When ever you go into WOT in a obd2 vehicle it goes into OPEN LOOP. You’ll still get readings but they are not inputs anymore they are solely a measuring device. Until WOT is disabled.

great , thank you man !

So A/F wideband sensor is more like analog vs digital. Analog has fluid scale when O2 sensor is just on/off. By the way the way you explain things is the best i have seen on YT.

Dan is the man....maaaan!

I'll put a new o2 thank you! Love your videos. Don't change that drawing board lol.

I have a 1996 Jeep GC with the 5.2 V-8, I had a problem about mid temp warm-up [about 150] on temp gauge check engine light, when I upgraded/changed to the Bosch Wide Band haven't had 1 problem in at least 5 years, I did a lot of reading prior to installing

Good info

Thanks

There seem to be times more often of late, I'm finding that at least for some cases, I should have been or should become a "Parts Changer"... Most recently, I found a vacuum leak on the intake manifold of an old Cadillac Northstar engine. I bought and replaced that gasket set, which did improve the performance BUT the fuel trims were still heavily pointing to a vacuum leak... Further testing showed that the PCV foul air hose connector at the manifold is leaking too! This part is listed at the same place I bought the intake gaskets from, and it's only $8.36... I saw that when I bought the intake gaskets, but I hadn't proven it to be bad then, but now that I need 1, I'll have to pay more in shipping than the parts cost, & had I just bought it with the gaskets, I'd have saved the extra shipping costs. Lesson learned is sometimes it's OK to change parts - especially if they are cheap and the old parts are 17+ years old!

Dam good tutorial well explained.. You remind me of a scannerdaner.. You think you can explain other automotive systems in this manner? Like evap, egr. Abs, to name a few ,incase u run out of ideas. Subscribed

Yes that's where they're going with this. Broad band just makes sense. Gives the PCM more information to work with. The old sensors were too slow and didn't "see" as much. And also couldn't respond as quickly over all engine operating conditions. The key to knowing what the engine is doing is what's coming out the exhaust.

good video

Rear oxygen sensors (or air/fuel sensors) are also used to adjust fuel trims. It's called fore aft oxygen sensor control (FAOSC). When everything is working fine, in normal driving, the rears provide little correction: GM material says less than 1.0% Ford says 0.5% Toyota says 2.0% But when something is wrong you can see up to 30% correction in fuel trim from the rear O2S in abnormal conditions. It's a weighted correction. So you won't see it instantly on a scan tool. You need access to vendor specific ecu data to see the stored value.

I use his fuel trim videos for training at my shop.

Schroeder you are the spitting image of all my instructors when i went to uti(honorstudent/grad) its soo funny how they/you we're spot on about auto zone Parts changers that blame computers when they're first guess didnt work and how you should run heavier weight oil after 100k....i got a question though...how much of a "learned drive cycle"does my obd1 toyota 22re have ?how smart were obd1 s? My yota has a very faint hunting idle. Ive been to the very bottom of my fullest drawer. Many times with this truck it was neglected badly when i bought it i pulled the head and took it to the old machinist dude at carquest who makes you apreciate what craftsmanship is all about ive gone through every fuel and emission system on this thing its starting to run like a yota again but even the fsm and other books arent this in depth ..thoughts?

Thanks for sharing your wisdom. I,m stumped on a 2008 Suburu DTC P2097. Live frame readouts for O2 sensor #1 is 2.355 volts and sencor #2 is .765 volts at idle. . P2097 is rich post catylitic fuel trim. STFT is 3.9 percent and LTFT is 7.0 percent. MAP is 4.0 and MAF is .01. I,m missing something , old school carburator guy.

thanks

I was always told that the downstream sensor does not affect fuel trims or mileage and that is Not true! The first purpose of the downstream 02 sensor is to measure cat efficiency. The second function is downstream fuel control. This function adjusts the upstream 02 goal voltage within the range of operation of the upstream sensor. The upstream goal voltage is used to ensure long cat life by allowing the PCM to control the amount of air and fuel that is supplied to the cat. If the downstream 02 sensor switch point is at a low voltage the PCM will adjust the upstream 02 goal voltage to reduce high 02 content by . If the downstream 02 sensor switch points stays high, the upstream 02 sensor goal voltage will change and allow a low 02 content. My downstream was fixed in the rich position and the fuel trims were pulling back like 25 percent and no codes being set. Shade tree in training attempting to graduate parts changing status! Great videos here! Show less

You're getting more comfortable > as I sit in my recliner on my front patio 🤣

from Peru 👍👍👍

🔥

I love you videos

Do the wideband A/F sensors make their own current, or do they require a baseline 5V input to work? Do they compare A/F ratios inside the exhaust vs the ambient air outside?

my o2 sensor behind the cat reports lean mixture or below 0.45v. this causes my car to go really rich and the wideband and factory AF sesnor reports ~13.9 AFR at idle. my fuel trims are +/- 2%. I haven't found an exhaust leak and the catalyst doesn't rattle or anything. is the rear o2 sensor bad? the voltage reported is not flat line, but its nearly flat at 0.1v. revving the engine hard does bring it up to 0.7v momentarily but it goes back to really low voltage at idle even with this rich condition.

hi.. I checked the part number. It is the same. I also removed the sensor and checked ecu OX pin voltage (open circuit). Still the same voltage 2.3 v showed. may i know whether it is a normal bias voltage? this voltage is coming from ecu and ecu circuit shows OX pin connected to ecu resister then geounded inside ecu. between ecu resister inside and ox pin voltage comparator.

Hi I want to ask a question about O2% sensors and how to get ARF values from it. I have Innovate LC-2 sensor driver. And It only shows me O2% And I want to read AFR from it. Do you know anything about the formula or conversation about it ?

Looks like a sign wave on a scope above center line is positive and below center line or zero is negative and reading amplitude .

I just found your channel. It's awesome information. Way better than asking for help on a forum. I would love to see a video on how to diagnose a bad O2 sensor that is after the converter. From what I understand is that the waveform of the sensor after the cat looks a lot different from the waveform of the o2 sensor before the cat. Reason being that the cat has corrected alot of the exaust gases. I know that if the waveform of both sensors look the same that the cat is probably bad, but how do you know if the o2 sensor after the cat is bad?

Matt, as much as I love to think test before i replace anything, i am stuck on this 07 Infiniti M35. Friend drove down the road and huge loss of power. Scanned it and ONLY P0300 with no specific cylinders. Frend took it to a nearby shop from the breakdown point. Spark plugs were bad (never replace at 170000mi) so they said "well, spark plugs need replaced anyway lol" & they dollow through with non-oem plugs as well as an intake boot. Still misfiring with burning hot exhaust. This shop sents him to a muffler shop & the original cats are cut but... same oucome. Hum Car comes to me. Scan it with my Autel scantool & noticed the fuel trim on bank 2 is quite high. I decided to go further & use the Power Balance feature to disable each cylinder at a time & quickly notice that Cylinder 2,4 & 6 cause no disturbance thus bank2 is where my issue is. Not wanting to switch parts over and over, I decide to start with compression test to eliminate internal engine/timing issue from my check list. Compression checks out okay. Spark plugs being non-oem, lets install what it is supposed to come with. Tested ignition spark with a spatk tester and got strong consistent spark at all 6 cylinders. LtFT is at 9.7% on bank2 and bank1 Stft is at 25% on bank2 but at 4% on bank1. Idling speed is 1000rpm at all time MaF reads quite high at 7.7g/s Increasing rpm to 2000-3000 rpm put the LTFT bank2 at 0% which makes me think of a vaccum leak. I almost washed bank2 with carb cleaner in vain then sprayed everywhere on the intake with the same outcome. Propane => same thing ughr Smokepro I purchased after watching your video on it, no leak whatsoever on the intake. Removed the upper and lower intake plenum last night to get to the injectors in order to check injector pulses with my noid lights. Positive injector pulses at all bank2 injectors. Tomorrow, i plan to check spraying patterns. At this point im checking everything....

first of all thanks for every thing you present it's amusing and i have question why diagram of air fuel ratio sensor is opposite of the diagram of O2 sensor i mean the richness in O2 sensor is up but in A/F ratio sensor is down

hi yes its different here in uk , they lowered emission but our roads are full of cars between 10 and 20 years old which at the time past emission with no problem , now they are just on the limits, there is nothing wrong with them .its their age that is killing them , my newest car is 10 years old my oldest is 20 years old , so emission days is doing everything oil change, air filter , clean air flow meter , check lamba sensors are switching , then cross your fingers

Hey man great video, love your stuff (except the subie bashing, maybe try a wrx sti?) Anyway I got a random flat spot at like 0v in the o2 sensor a couple times for about 20 seconds straight around 2500 rpm. The LTFT was around 4 and the short term was at about 1 when it happened. Other than that, the o2 sensor was oscillating fine at .1 to .9, any thoughts from you or anyone as to what happened? My software is pretty crappy, but didn't show anything out of the ordinary on 2 other cars

Is the downstream O2 sensor said to be working fine if it has constant value at around 0.7 or 0.8 volts? also does this mean the catalytic converter efficiency is good?

Thanks for the soda.

Hey Matt, enjoy your videos. I was a Ca. Lic. smog Tech for 25 years. Worked at indie shops and Nissan for 8 years. My college teacher gave me a great way to think about O2 sensors. Voltage is the potential difference in electrons. So a O2 sensor measures the potential difference between inside exhaust Oxygen and outside ambient Oxygen. So, Lean cond = more O2 in exhaust, and when compared to outside O2, it has a low difference (or potential) therefore low voltage. Thus, rich cond.= low O2 levels in exhaust and when compared to outside O2- bigger difference, higher voltage. Just wanted to clear that up. Oxygen sensor only measures Oxygen. BTW, my hobby is Quantum Mechanics too. At Nissan, we were told to look at .001 voltage fluctuations for a/f sensors, a long way from mV. Also same college teacher had us looking at O2 sensor crosscounts to see if O2 was biased one way or other. Good Luck, Alan.

A/f wideband vs o2 sensor. In other words do you mean wideband vs narrowband o2 sensor. I am not machanic but I am addicted to your videos. I watch them time and again because I want to grasp the concept Moshitoa from south Africa

Thanks Matt! Good information here! Mmmm in fo maaaa tion Mmmmmmm.

God bless you. I think you have been collecting all of those manuals so I can restore old cars. I'm pretty sure that was gods plan

To answer your question regarding expensive DVM's, it's not necessarily the precision of the DVM as much as its ability to handle power. They are primarily meant for electrical work, not electronics as in this application. The expensive ones (i.e. Fluke) are typically used on high voltage circuits. The power racks for the equipment I work on can be anywhere between 208V to 480V operating on 600A contactors. The facilities electricians work at even higher voltages and powers. There are occasions where live electrical troubleshooting is required and the DVM's that we use have to be rated for it. Test leads also tend to run expensive as well as they also have to be rated for the power that you are measuring. This means that you are paying for the ability to handle power and not necessarily getting a more accurate reading. Additionally, to measure current, you will either need a clamp meter or the test leads will have to be in series with the circuit (more accurate than a clamp probe), not easy to do in most situations.