Diagnosis and Understanding: MAF Sensor Pt1 Analog, Digital, Hotwire, P0101 P0102... 

There are zillions of youtubers with their massively edited useless videos and on the other side there is this boy who is killing it with a micro white board and pen

Absolutely on point explanations. First class educational video, just what is needed on RU-vid. No techno babble, no pie-in-the sky theory, just sound detailed advice.

I'm in awe at your ability to explain all of this so clearly. Thank you so much and please - keep these videos comin'!

As a friend once said, there are plenty of parts swappers in the world but few true mechanics. You sir, are a mechanic. Thanks you for the education!

If only more people (including many professionals) would watch your diagnosis and understanding videos they would really up their game to another level! To be honest Matt all of your diagnosis and understanding videos on engine management systems are the best on these subjects. You have a unique teaching ability that even diyers can easily understand. Such a shame that more people do not take advantage from what you are offering ...

Dear Matt. Thanks for all the fantastic videos. I have watched 1000´s of hours of Automotive DIY videos on RU-vid, but I find your videos the most informative, and I love your scientific approach. Many thanks.

Just 4 minutes in, and subscribed. As an engineer (but very illiterate about cars), your style totally resonates with me. I'm hoping this video will answer my questions about my car's bad MAF sensor that I am currently dealing with, so I can make an educated decision.

The best car video channel on youtube Matt, I learned many things from your videos about sensors & many other things which you always talking about in middle of your videos, I'm not a mechanic, just an ordinary guy who like cars & watch you from Saudi Arabia, Big like & big thanks Matt, You are the best ...

I realy would agree that your video of fuel trim is by far the single most fascinating of all on thr internet. So simple, yet so very complex. Awesome, just a brilliant upload.

Love the way u explain things in very simplified way and quick to understand We need good people like u in our society. Thanks Matt

Thanks I spent 400$+ on my car for codes at AutoZone and watch your fuel trim videos and bought a 120$ Bosch scan tool and found out it was a intake leak and not ant of my sensors but now I know thanks to u

You make fantastic videos for us DIY guys who don't want to pay someone $100 an hour to guess and throw parts at our car. Thank you very much!

Thank you for your Diagnosis and Understanding videos. Your explanations are really clear even for a French who don't speak english fluently.

This is an absolutely fantastic video and education! When you have a great teacher its incredible how exciting the learning experience can become for the student and how far they might go. What a great feeling it is to truly begin to understand how things really work! THANK YOU for taking the time to teach us as you do!

There IS no easy way around it. But the time you take to watch these videos will give you an understanding of how these modern engines run. It will also save you a ton of money buying parts YOU DON'T NEED and actually zeroing in on the cause of the problem. I.E... the CHECK ENGINE light comes on. An error code trips it.... could be an O2 sensor. But it doesn't mean the O2 sensor is bad necessarily. There are many reasons an O2 sensor will send an error code. This applies to many other sensor and codes also. This is the value of Matts videos. If you LIKE buying parts you don't need, chances are good you'll be gone in 5 minutes. But believe me man....I used to do EVERYTHING on the old pre-ECM engines. Early '80's. V-8's, Slant 6's, Straight 6's, 4 bangers. Could do anything on them. Blindfolded. Then....I lost my garage due to divorce moved to L.A. I didn't open a hood in 2+ decades. In 2017 I bought a 2005 500 Limited with the 3.0L Duratec DOHC V-6. When I opened the hood I didn't know what I was looking at. It was a WTF moment FOR SURE!! But I knew, bottom line, it was still AN ENGINE. I bounced around RU-vid, watched lots of "HOW TO" videos and bought parts that did NOTHING. Cleared the Check Engine Light and thought I was good. A few days later the light would come back on WITH THE SAME CODE!! So frustrating man. Then, thankfully, I found this channel and learned more than I could ever tell you here and I still am. But I'm not intimidated by these engines anymore because of Matt. Doing my own work again and come back often for refreshers. The best automotive channel on RU-vid HANDS DOWN on understanding the WHY instead of the HOW to do a job. A huge difference. Thanks A MILLION buddy!!

My New Favorite Chanel , Absolutely a wealth of knowledge on how the sensors operate & Correlate with each other And the proper way to diagnose my Vehicle, THANK YOU Matt !!!!!

great video. Ive met alot guys who don't understand the science and logic behind it all. they just know how to swap various parts out quick enough to make the boss happy. they don't even wanna touch it. might hurt they're heads from to much thinking

FYI. It's not necessary to have an oscope to read the frequency signals. A fluke 289 will read the frequency, amplitude and duty cycle and even read PWM all on one screen in numerical values. Not as good as an oscope. I have an oscope too but it's AC powered with I think tends to induce unwanted noise into the trace. I would like to get a snapon modis. Love the videos, great job.

Thanks for this analysis. II ended up replacing the MAF Sensor to no avail. Your explanations video help demonstrate how a trouble shooting diagnosis procedure can improve. The symptom was the engine turning and starting before shutting right off. Unplugging the Mass Air Flow Sensor made the 3.3 GM V 6 run okay. At some point I looked over everything I touched when trying to figure out how to access spark plugs for cylinders 1 3 and 5. Upon doing so I noticed a loose bolt that was securing a vacuum source that I learned to identify after referencing the service manual. The following day I heard a hissing sound and found a broken tube that connects to the evaporator canister. I used electrical tape to help provide a seal to the bolt attached to the vacuum source since i over torqued it and bent the piece inward. Then I used electrical tape to help secure the vacuum hose leading to the evaporator canister. The car finally starts up and idles okay. Now there is a DTC 22 (Throttle Postion Low) that I am waiting to see if it goes away after driving and re- learning by the computer now that there are little to no vacuum leaks.

I am an auto repair professional. I was using your very informative MAF videos to help me with a particular diagnosis. You talk about 3-wire, 4-wire, and more sensors. I have made an image for a MAF connector for a 5-wire MAF on the VW Jetta I'm working on. The pinout works like this: PIN #1: IAT SIGNAL; PIN #2: B+ FROM FUEL PUMP RELAY; PIN #3: ECM LOW REFERENCE (-); PIN #4 VREF ECM +5VDC; PIN #5: MAF SIGNAL. I can't offer the image in the comments, but I can offer it to you if you like.

Good shit! I heard a woman on a video on your ch. call you 'Mr. Molecular Biologist!" You must be a prof. What do you study? I'm SO glad I came upon this resource. I'm brand new to autos. I was a research tech. in Biomed. @ Pitt. I've learned SO much compared to any other auto vids. I've watched. And, I've only watched 4 so far!. Thanks, again. Looking forward to it!

These are the kind of videos I like. Very informative, reminds me of A/C Tech School.

You're the best man ! Real teachers / instructors, should be jealous .

There really ain’t words that say holy shit thank you enough! Your fuel trim vids are enlightening at the very least. I’m sold on your channel, 5 thumbs up!

Automobile systems mastery training. Like a boss! Thank you sir!

Got an issue with a MAF sensor on my Ford, so I kicked off by searching for videos on MAF sensor testing. What was I thinking? When will I learn that, for proper diagnosis of engine faults, there's really only one guy. Ok, ScannerDanner is good, but this guy takes the biscuit. It almost seems ironic that the best automotive teacher on RU-vid is also the most under-rated. Forget the others, just filter your search results to include only those from Schrödinger's Box.

The people who come up with these ideas are.............engineers! I are wun! Good teaching sir.

i found that the vaf sensors are quite reliable (i think i replaced four in 28 years, three had bad fuel pump switches, never had problems with carbon build up) i think the biggest drawback is slow response time and i suspect they are more expensive to manufacture.

Before I move onto part2 I just want to let you know Matt that I appreciate what you are doing. I like how you are getting at the fundamentals. I have always learned best by getting a good grasp of how something works and then the troubleshooting just comes naturally in my case. Like Danthecarman said your explanation, the way you break it down is spot on and it makes it so much easier. I was going to join the scannerdanner monthly subscription and I still may, but for where I am at as far as knowledge right now, I think your channel is going to help me out more. I'll soon be joining your monthly subscription. Take care!

Man u Are Mechanincal Professor Respect From Pakistan

The frequency can be easilly be measured by your ear with small speaker connected thru 1k/10k resistor. You will simply hear the frequency. This is usefull for those who doesnt have an osciloscope.

Most common DVOM's will only do 1 second refresh rates (1 Hz). That means you can only have 1 signal change per second. Any faster than that and the DVOM is no longer reliable and only an oscilloscope will be able to measure the digital signal. Understanding electronic concepts such as frequency, amplitude, and modulation is crucial in understanding the limitations of using a DVOM on things like a digital MAF or O2. Comes down to the right tool for the right job. You wouldn't use a screwdriver where a sledge hammer is needed right? Brilliant video so far. Really enjoying this.

Thank you !!! You are amazing good to explain theese things. From this video i finaly understand why, in my Peugeot 207, the MAF voltage was 2,5v compare to the ground and 10v aproximatively compare to 12,5 Volts of battery. Because is a Frequency MAF. I have installed a kind of device for controlling some sensors , for increase the mileage.( That's because i have installed a HHO Hydrogen cell on my car ). Now i will try to connect that device to MAP sensor and the second IAT sensor who are near the intake engine. ( it is the first IAT, near the MAF , after the air filter) . First i will verify if the MAP have a voltage output... I can't find the Oxygen sensor(s) in this car. Or maybe they don't exist. It's a Peugeot 207, 1600cc , 110 HP , Turbo-Diesel , 2006.

You're a good teacher Matt. Your explanation was clearly and easy to understand. Thanks for information sharing I hope you're getting well.

now I know what is the different between the analog and digital signals and how to understand each one, Big thank you matte now I am going to watch part 2.

Guess im the only non advanced diy mechanic who listens to this but this is awesome, thanks !

It's a mistery for me how a man so smart, and who can talk so rapidly, and without verbal mistakes, can have such a bad writing. 🤣. Anyway, thank you for all new things that i am learning from you every video!

awesome explanation. You should explain how the MAF produces the 1-5 volt signal back to the ECM in relationship to air flow past the Hot wire.. You explain how the Hot wire receives varying current to maintain a certain temperature via the 12v wire. But what does the 5v reference get processed with in order to send the relative signal back to the ECM?

Man, you are a national treasure !

Hey Matt, I'm new to you're channel. Watched a couple videos and plan on watching the rest. Great extensive knowledge. Awesome how you go in depth and make it easy to understand. Good attitude good videos keep up the great work! You the man

Very great presentation. More mechanics need this kind if training especially in my country. Very few goes to school or have formal training. Your at there mercies and when you do find a good mechanic you have to pay through your nose. Thanks for making theae video.

I cameback to rewatch this after your recent MAF videos. There is nothing that scares me more than not knowing what the maf reading should be. In diesel they operate differently, I guess.

thanks for this VIDEO! It seems a faulty/aged MAF sensor is creating a random P0300. I cleaned it initially- but finally just installed a new one yesterday and the performance is appreciable. Less $$ than I thought. DIY.

Great video with excellent and comprehensive explanation. My thanks and appreciation.

Anyone else catch that he introduced himself as MAF? Nice Freudian Slip...not a true one, but the phrase has slowly changed to mean that something you're mind is working on came out. So cool. :) Purposeful or not. Spoiler alert didn't ruin anything. As you hinted at 7:20 about about another non scan tool test I was all smiles. :)

This guy is an awesome teacher professor!!!

you've enlightened a lot of viewers, thank you...

Killer video! Great info with detailed explanations that I could actually keep up with! Thanks!

I'm an ASE Master Certified mechanic and I think your videos are great. Let me know when you come out with a box set

Your english is very clear,keep it up

Your vedios are very useful to me in diagnosis. Thanks a lot

Massive knawledge man! I yelled out potentiometer when you mentioned vane sensor lol

I just cleaned my MAF by removing it and and spraying it with CRC electronics cleaner and no wiping or touching the wires on a Ford Windstar 2003 model with a 3.8 engine and the difference in idle was dramatic in a good way. I had just within the last month replaced the head on the front side of the motor because of a burnt and leaking exhaust valve , the idle after the head replacement was good but not right. Eventually the engine light came on (after 500 miles) and I got a code of PO 174......I would suggest doing this cleaning before replacing the MAF itself as they can be pretty exspensive...instead I spent nine dollars for the spray from CRC which leaves no residue.....The sensor is the first to affect engine idle ...and if it doesn't solve a rough idle you can move onto oxygen sensors or gasket/PVC leaks etc... in my case it was dirty wires on the MAF...just an option for you all

Sir u r more than a professional. Pretty clearly elaborated all the possibilities. That's really wonderful actually Goodness me your energy level is absolute remarkable more than a Boss

very educative. Thank you regards

awesome REM reference

Hello Matt!! Excellent stuff!!! At 6:22 the engine does not maintain stoich. at all times, it runs lean at decel, rich at WOT and most vtec and direct injection engines work lean at partial loads low rpms... In fact the more advanced the engine, the less time it operates at stoich and homogeneous combustion (as lean modes require stratified mode as you most likely know)... Just a thought! Cheers!! PS: i'm inclined to watch the fuel trim video (it is the best) with my classroom... will give you feedback if i do so...

I haven’t heard about “Kenneth“ and “what’s the frequency” in YEARS!!

Wow!! Amazing!! I’m hooked on your videos

love your knowledge skills wish there were more techs this way that could help me. i could really use you input on my car issue .

Awesome videos. Will watch and study all of them. Love knowing how thing work.

Such a great explanation. Thank you so much. I can’t wait to see part 2.

I enjoy all of your videos. Very informative and helpful. Keep it up

Very well explained , i love it. Love all your videos .

u reminded me with my first lesson in telecom engineering 🥰 now im studying mechnical

Max has the right idea but I think the explanation is slightly off. I would say that square wave pattern will change. At higher air flow, the MAF would have to be supplied hear for longer higher voltage would be sent to MAF for longer duration and for less flow, for shorter duration. So the shape of the square wave would change. I would guess that the frequency would be the fundamental frequency of the fourier series or FFT of the wave form. Thanks for bringing great videos Max

Thanks Matthew.

my multi-meter has several added features for measuring: Auto-range, Temperature, Frequency, testing Diodes... I got it as a gift, but I think it was fairly expensive.

Always a pleasure !

Very good video. Thanks

When I did put it on the OBD it shows perfect no alms no engine check light. But the full story is. I bought it it used to be so hot. I thiought it was because the engine wss uder the seat. So I bought insulation material and insulated it. Helped alot but the heat was under there. Sometimes your going up a hill and it just will not go. The engine is not reving. It comes very slow then after almist coming to a stop it picks up and shoots off fast quickly changes out and start going slow again with engine not talking the rev. Also it is drinking that gas like a hole is in the tank. When its drinking this way its hot. When the mileage is good enginenis so cool you never need to insulate it . So its a sometimes situation. I do not think its a oxygen leak but it behaves like its not getting the right ratio of fuel and air. Cause engine is not reving out . When your parked it will rev out but not very quickly its respond but not fast. Slowly revs up not quickly.it has me really puzxled. Also because it was doing this I check the catalist and found it blocked up. I removed it completely. Then imediately engine light came on saying the catalist is not woring. I place a adopter inside it to fool the compter the cat was still inside and it removed the check engine light. But its same drinking gas and not respoding when hotnor going up a hill. If you stop and move off it does ok then slows down as it changes out and go back to a walk then after this it shoots off again and repeat it all the time. The upstream 02 sensor or cat monitio is a four wire and when I plug it into the conector and turn the ignition on and hold it in my hand it is mit heating up at all. However the the top one closest to the exhaust called the fuel air ratio sensor warms up in my hard as soon as the ignition is turned on. Hope you can.help me. Nof aure if both shoild work same way. Both os four wire so I imagine both has a heating circuit. But the sown stream one mot getting warm.

I just solved an issue that was being caused by the MAF not having a screen in front of the sensor. I have a K&N intake system but they don't put the screens in them. Car was running poorly at light throttle. I remember that being mentioned here so I bought a piece of aluminum honeycomb material and made a screen for it and the problem went away. Thanks for the video.

Some voltmeters can measure frequency and duty cycle.

Thank you!!! Very easy to understand and I have a hard time learning.

your presentation is very good ..thanks

Great videos, keep up the good work.I have enjoyed every one !

And don't forget to acknowledge that the tools require subscription and constant updates.

Dear Matt Many thanks for your afford and the informations you shared with us. I have been searching the net for a long time and I haven't found the detailed and well structured infos like you share. Please add some about diesels especially. Since I am driving a Ford Kuga (MY2013/ 2.0 tdci AWD) and having troubles with hesitation at low rpms (like after giving a way in a roundabout) Again many thanks

i really appreciate videos like this,thank u sir

Newer Digital Multitester was now have frequency measurement function and we can use it to measure frequency output of MAF Sensor.. example Fluke 17B+ Multitester.

You are good teacher thanks to share God bless you

Hot wire MAF is actually a resistor that gets energized and the resistance value changes upon heat dissipation from incoming air. Probably a thermistor same as the coolant temp sensor? I'd be interested to see a MAF dissected.

I got one im my shop i wish you could go through. 2016 mazda 6. P0171. Ltft is stuck at 20.3 and stft 10+ the fuels trims stay this lean at idle and when increasing throttle, they are always like this. Low side Fuel pressure is good (65psi at idle), high pressure fuel pump is good (actual vs desired right on spec), all input sensors are good with normal readings, no vacuum leaks, pcv system is good, purge valve is good not stuck open causing more vaccun. I ran it on fuel injection machine in the fuel rail to eliminate bad gas or something, fuel trims stayed the same. AF ratio sesnor is good, maf has been replaced with factory maf, no change, always reads in spec. Vehicle has a map sensor also, readings from that are on spec also. Im at a complete loss at this point. Oh the fuel injectors are very clean, as seen with boroscope, as they should as I ran fuel injecton cleaner through it. I don't know what to do at this point....

Fantastic video, thank you

my 05 silverado threw the code P0102 so i immediately went out and bought a new one...just kidding haha. surprised i missed this video.

Thanks for an extremely thoughtful & through explanation. I was having trouble understanding the hertz output but I think I do now. I will watch this video many more times.

Hello, thank's a lot for sharing your knowledge i really appreciate it you had teach Me so much in a so simple way that i have become a much better diagnostician thank's to you keep up the good work blessings!!!

Excellent. Congratulations!

Another great video with lots of good information! I haven't run into one of these vortex sensors yet; looks like I'm gonna have to do some research! I think I might have heard something about their existence in passing several years ago, but that's it. On an interesting side note, your mention of O2 sensors reminded me... Pick up an old (or new) analog voltmeter! I think Harbor Frot still sells them. Scopes and GMMs are nice and all, but sometimes it's easier to just toss an old analog meter on the thing. It's definitely cheaper, especially for the DIY guy that doesn't want to drop $1,000 on a low-end scope. :)

amazing.... amazing ....amazing.... Thank you very very much ....

thank you for your time and effort.learning alot

Brilliant video! Thank you!

Love this video bro

your awsome man thank you so much

really good teaching. thank you so much

Will also be purchasing the Autoingenuity scanner program.

5:33 and also hydrocarbon. lol yeah we know what that look was about. fond memories.

Appreciated 👍 very well done and good explanation very simple and to the point . I have a problem if you can help me out please , It’s a Range Rover sport 2010 3.0 diesel. 1-Starts straight away 2-engine light is on and it’s on limp mode 3- throwing code p0193 4-change the high pressure fuel rail including the sensor 5-changed map and maf sensors 6-car won’t rev past 3 7-max speed goes up to 70mph 8-drops the rev and speed when going uphill 9-sometimes on a flat road it drops the speed to 20mph and rev won’t past 2 10-recently got it services and changed all the filters including fuel filter . 11-i have got a cheap OBD scanner and saw a fuel pressure on live data it shows 22000 and it’s still won’t go up and down when rev . 12-when sudden floor the gas paddle it will drop the speed rev won’t go up it feels like fuel not coming or exhaust is blocked ,fuel or exhaust system feel squeezed .but if rev it slowly /gradually then it picks up speed until I floor the peddle but when release the paddle half way up then it feels bit of ease . 13-sorry for the very long message but I wanted some help desperately and wanted to describe as much as possible .been to land hover specialist and few other garages but no joy ,some say it’s an electric issue and some say it’s a high school reassure fuel pump and some say it’s a turbo or pcm issue but no 1 is able to figure it out exactly .. ( I have a short video uploaded as well on RU-vid ) any help would be appreciated.👍

LMAO! What's the frequency Kenneth, is your Benz a dream? Phenomenal song reference! Love your vids even more now. Keep up the vids AND the pop culture refs please.

Here is my problem. 04 GMC Jimmy 4.3 vortec. Banks 1&2 read rich. MAF shows 10g/s. Fuel trims show -25. Replaced MAF and replaced spider fuel injection. Still shows same reading. I’m thinking the IAC valve is allowing more air to pass the throttle plate which shows the high reading on the MaF. No IAC codes though.