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MAF Sensor Testing- What REALLY Matters
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- Опубликовано: 4 ноя 2022
- Join us in the classroom for this quick lecture on Mass Airflow Sensors. This is a portion of a full length lecture from my book. For more lectures and additional case studies, join us over at ScannerDanner Premium! We have a 14 day free trial!
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For more information on this topic, I have written a “field manual” called Engine Performance Diagnostics which is available at www.scannerdanner.com as an eBook or paper book.
Want even more diagnostic training? Whether you are a DIY trying to fix your own car, someone looking to become an auto technician, or a current auto technician that wants to get more into diagnostics, subscribe to ScannerDanner Premium www.scannerdanner.com/join-sc... There is a 14 day free trial.
On ScannerDanner Premium I will bring you right into my classroom at Rosedale Technical College. You will find page for page lectures taken right from my book as well as exclusive classroom type case studies. What is so special about these classroom case studies? I pull live problem vehicles directly into my classroom and we troubleshoot them in real time, using and applying the theory and testing procedures we learn during the classroom lectures. There is no better on-line training of how to troubleshoot automotive electrical and electronics systems anywhere!
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Thank you! Look forward to seeing you there!
@@ScannerDanner
Done. 👊🏻😎👊🏻
Sending hello from Israel 🇮🇱
@@ETAI106 awesome! Even better where you're from!
I can’t put in my credit card info, I checked everything and it kept saying that it failed
@Lowell Evans Lomboy where are you from? What country? Email me at support@scannerdanner.com and we can help you.
I have said it before and I will say it again ............... Paul I wish i'd had you teaching me thirty years ago because like you said most of the teaching material was all focused on how they were made and what happened inside.................. NOTHING about testing on the vehicle which was absolutely useless in the workshop. I really wish I could shake your hand and thank you in person. You are a great man. Thank you.
I wholeheartedly agree you are a great teacher without a doubt.
@ScanneDanner is a Master 👌
His explanations are pure gold , ty for sharing your knowledge with us !
Thank you Jose
Great description detailing the operating conditions that a MAF works in. Didn't realize it was a self-contained module and not just a "dumb" sensor.
Years ago I had a 1993 Merc Marquis with the 4.6 that ran like crap and bogged down on full-throttle. I checked the MAF and the hot wire resistor looked like a tiny Q-Tip. I blew it out with shop air and ran some contact cleaner over it. It ran like a Mustang after that! Amazing what a little bit of fluff can do to the running state of a vehicle. Since then, anytime I diagnose a poor running engine I always check the MAF first. Sometimes the simplest check is the best solution.
Working on a Saab 93 right now with a bad maf sensor. This is good stuff with perfect timing. Thanks Danner
I was always reluctant to try learning the electrical side of cars, UNTIL i found your channel. The way you breakdown the basics, its not complicated at all👍. I wish i had teachers like you when i was in school
Thank you so much! I'm really happy to hear this type of feedback.
I’ve now watched quite a few of your lectures and I’d just like to say your ability to explain and help understand is fantastic, you are a great tutor, I hope your students appreciate that having knowledge is one thing but the ability to explain and teach that knowledge is a skill by itself. Hats off to you sir here from the uk 👌👌👌👌👍 many thanks for your videos
Wow, thank you!
Good teaching makes makes complex stuff seem easy!! Good teaching Paul!
“If you can't explain it to a six year old, you don't understand it yourself.”
― Albert Einstein
Very good Explanation ON how a Maf Sensor works resistors are also Cooled by the air so they don't over heat 2khz to 10khz is a pretty standard speed for most Resistive Systems @ScannerDanner
Yep you have to have 5 volts on a 5v pull down Circuit knowing the Circuit is key to Finding the correct Problem and Finding the correct failed Component and Maf get contaminated alot great Video as always Brother @ScannerDanner
Really good class Paul! Soon I'll be watching the full class! Thank you and we appreciate everything you have done for us!
Premium 100% People....Get it.!
Love that classroom study...still one of my favorites to watch. Thanks BrotherMan..Now I have to go and finish watching this one. Lol Cheers
Very good video, always educating us. 🙏🏻
Excellent info Paul. Had one recently just like that turned out to be poor connection at ECM feeding the 5V ref. signal to the MAF. Thought I'd better check the ref. voltage before I replace the MAF and glad I did.
Thank you.
Mike
Pure Gold . Thanks mate !
I am always watching your video for my students
Man its crazy how your teaching makes understanding this easy
Thank you so much!
Excellent explanation of the MAF operation. Than you.
Thank Danner, you gave me something to look at since i have been getting p0171, p0174 intermittent codes. It's a couple month old HP MAF Sensor from Granatelli.
Thanks for sharing Paul. Cheers.
Great class Paul, thanks for share.
Great explanation Ty keep the videos coming
Your the teacher that I lost 60 plus years old and you open my eyes to the future in engine D/A emission control fuel management need instructors like you and out off all things that verse from the book of PROVERBS 22 : 29 it is a verse that gives power to me when I Woking on a car because off age brake down the work to serviceing and engine management D/A and electrical 👍🇯🇲
Love that verse! My mom always quoted that one to me. Thank you!
Real talk as always! 👍
Thank you Paul.
Great information. Thank you.
Thank you for that information.
One thing I've always remembered from one of your old field trip videos is a "rich at rest, lean under load" pattern with a bad MAF. I've always assumed that was because the computer notices the rich at rest part of it so LTFT is reduced, triggering lean codes with driving. It's almost as though the slope of the recipe for adding fuel is wrong, because of the blanket of dirt on the resistor. I'll never forget the way you made the diagnosis one day from the drivers seat with your students in the back. You simply watched STFT while stomping on the gas pedal. Vac leaks improve when adding fuel, MAF-induced lean problems get worse, as do fuel delivery problems. That car kept falling on its face when you tried to get your kids back to the shop.
Thanks again Danner
You're a killer Danner!!! Good job explaining all that stuff.
Thank you!
nice job Dan
I love the way you present these videos, thank you. In the video, the 12V feed heats the resistive element. Unless that 12V is a regulated supply, it is impractical to infer that the micro alters the current in the heater circuit with normal voltage fluctuations being 11 to 14.5V. If this were the case, and the heater current was adjusted to maintain a constant temp, then the sensor would not see any variation as the air flow increases. Also, heater element temp regulation adjusted by current flow would be a slow process, not fast enough for compensatory engine adjustment. It is more likely that the sensor wire portion determines the cooling delta read by the micro, which generates the variable frequency square wave output. The engine computer takes it from there. I stand to be corrected.
Some maf sensors have 6 wires with IAT sensor inside i have seen some with analog signal the measurment on signal wire is a little bit different but great video thanks for education videos we learn something new every day
Haha man I just had a check engine light came on
I scanned it and the health report came back with 48 codes..I almost touched cloth. now this vehicle 2003 Oldsmobile silhouette, very reliable for ME is 19 Years old with about 210K miles..
The first code listed was the Mass Air flow sensor so i went to work on that baby sprayed it cleaned it well,.also while I had the air intake off decided to clean the throttle body and then installed everything back.. cleared the code and it hasn't come back again
Another great fix was that intermittent tranny slip on first gear is totally gone.. That was one of the tranny codes..
Amazing how just cleaning the mass air flow sensor can fix so many codes lower down.. unbelievable hope this helps someone..
Great video ✌️✌️
These are hot wire anemometers. We used them to measure inlet air volume in jet engine testing.
That's awesome!
Re ground side pull down: When I took an IC class, I noticed that just about everything was fed hot (5v) and all switching was done on the ground side. Look at your ignition coils and fuel injectors. All had direct (battery) hot and the circuit is completed by a driver in the computer "driving it" to ground. I forget my Boolean, but any circuit/logic can be created using NAND chips...they ground everything to create the decision. And 10khz switching(?)... no mechanical switch is capable of that kind of switching. Transistors and chips opened up a whole world of possibilities. Young man...learn your electrics.
Dame wish I had you teaching me all them years ago when I started in this industry
Thanks Tom
Damn this guy is good thx man
When contamenets get stuck on the sensor changes the resistance which then runs Very Lean because it can't calculate the correct amount of air because the sensor is Covered @ScannerDanner
Thank you paul for the indeep knowledge that you giving.
Thanks
Hey, I'm the first person to comment. Well then, let me take advantage of my over forty years as a professional tech to give you my immeasurable amount of experience in testing MAF sensors. Wack it with your screwdriver handle. 🤣 Well, at least that was what you did back in the eighties when the 3.8 Buick came out. Just kidding (kinda) learn how they operate, don't over think it, have the right tools and know how to use them. And by all means take advantage of videos like this. I had nothing like that. My scope was taller than me and nearly wider than the car I was working on. Now my pico and fluke oscilloscopes along with a laptop will fit in the same tool bag. I still miss cylinder balance from the old scopes though. Oh well, can't have everything.
Do you discuss speed density using air temp and MAP ?
Something confusing. My 85 vette manual MAF, says it is a PULL UP RESISTOR. ??? 5V is required for test unplugged purple wire, with changes to .5 at idle and 4.7 at WOT because of the MAF air flow.
I remember when pertinent info like that 5 volt pull down circuit was in the wiring diagrams. Maybe some manufacturers still do that with simpler systems. It sure sped up diagnosis.
I'm confused, my c3500 has a 3 wire maf sensor I back probed with koeo, 1 wire had 5v , one wire was ground obviously the 3rd wire had nothing with koeo, I started the engine I still had 5v , ground, but on my 3rd wire i still had nothing on what i believe to be the signal wire from the maf to the ecm , so would that not mean the maf sensor is bad ?
Nope, you are missing a 12v feed. All MAFs have them. Your 5v is your signal wire if this is a GM
What about the solenoid sometimes cars in the car to go faster as opposed to slow is that the solenoid
Hi Paul. Do you have video for MAF hot film wire type sensor lecture or case video study
The only real difference with the hot film types is they were not cleanable. I can't remember if the signal circuit was analog or digital but either way, the testing is no different.
Volvo V70 01 through 07 uses 5v maf sensor :) and I'm 100% positive because I own a Volvo V70
Good stuff! With the lean codes, does that mean pcm controls more fuel to the engine?
This is how I see it:
With a dirty MAF, the PCM doesn't see as much air entering the engine but the O2 sees that the exhaust has more unburned Oxygen meaning the engine is actually running lean, so PCM adds fuel to get back to stoichiometric. This results in positive fuel trims and a MAF sensor DTC.
Edit: So the PCM checks the stoichiometry of the system (MAF accuracy) by checking the O2 signal. In other words, the PCM doesn't reduce or increase fuel injection based on MAF signal alone. But how does it know that the O2 signal is trustworthy (i.e. that the O2 is good)? By checking the O2 heater circuit resistance and how quickly the O2 signal switches from rich to lean within a specific short period (e.g. 5 times in 10s).If both MAF and O2 are untrustworthy then the PCM falls back to its in-built look up tables which contain expected values for different engine sensors at different operating conditions. And off course sets codes for offending sensors.
I'm not an expert by any means and your question prompted me to really think. Hope this helps.
The fuel trim trouble codes come from a fuel trim correction that is beyond the normal +/-10%
Typically about 16-20% is when you'll start seeing fuel trim codes. P0171 and P0174 you can expect to see positive trim numbers (adding fuel above the baseline fuel map), from a lean condition (lean O2/exhaust). P0172 and P0175 you can expect to see negative trim numbers (subtracting fuel below the baseline fuel map), from a rich condition (rich O2/exhaust).
@@abdul-kabiralegbe5660 Wow! Sure did ty!
@@ScannerDanner TY. I think I might be getting it! lol
@@chriscrusader5412 And thanks too to all those who've made automotive knowledge accessible here on RUclips and elsewhere.
so if paul talks into one how high will the hot air volume read ???? lol just kidding. love these class snippets.
Overheated for sure 🤣
more hot air than a dozen hot air balloons! 🤣🤣
Dear danner, you are my main teacher. But Toyota corolla 2019 do not have 12v power feed. It is 4 wire including the IAT sensor and digital MAF sensor signal. Check it your self . Hope to make a video for this vehicle
I'm curious about it being a pull down design. Wouldn't pull down default to 0v when unplugged? I was under the impression that pull up would be 5v in this case? Thanks, love the videos!
The sensor in this case is pulling the voltage down when it switches on. I'm calling that a pull-down design. Doesn't matter that it has a pull-up resistor in the ECM. I refuse to call the circuit "pull-up". It's an industry plague imo
@@ScannerDanner Thanks for the clarification. The way you teach it makes a lot more sense I was just confused because I've heard it the other way around. Great video and information as always.
Question:
Is the MAF sensor used as the thermometer in the truck as well?
On some models there will be an internal intake air temp sensor, yes. But it wouldn't be involved with any outside air temp reading for your climate control system if that is what you're asking. Separate sensor for that
Do you have a video explaining the situation where dirty MAF could lead to rich condition at idle?
Yes, it's on a Subaru on one of them and I think a Mitsubishi on another. Let me see if I can find it. I'd be in my chapter 12 playlist right here on YT
Hey Danner have 91 dakota I tried cleaning some of the grease off of and might have got water somewhere it shouldn't be. Anyways when I turn key to start and hear loud click or pop sound then all power is gone no lights on or anything. Have to unhook battery couple mins and rehook up and power comes back??? Any ideas of what to look for power and grounds to everything seems fine checked with test light
Check your main battery cables including the block ground connection and battery positive cable where it attaches too
Ok thanks I put test light on B+ and touched engine and it lit up but that probably don't mean anything because circuit has to be loaded right
@@Ohiogrown89 correct. Do that same test during cranking and tell me what that light does
Ok thanks I'll do that tomorrow on my day off
Big fan by way and subscribed to premium trying to learn from the man appreciate everything you do for all of us brother
Can you also have a pull-up circuit design. Where you would have just a few millivolts on the signal wire with the signal unplugged
Sure. But it would be a steady signal and not floating.
Today I had a mass air flow fault code. Tested wiring had 12 5 and earth. I miss understood the circuit and powered the earth via test light and resistor while watching the scan tool voltage for the mass air sensor which was always at 0 volts, when I did this it read a voltage,( i assumed the 0volts line was the signal wire)which indicated a mass air flow fault to me. Replaced and fault fixed.
Why did applying a small voltage to the earth make the scanner show a voltage I'm confused
0 volts or 0 grams per second?
@@ScannerDanner it showed grams and volts, substituted value if I went in through manufacturer but if I went in through obd there was zero grams and zero volts, so I powered what i thought was the signal line and watched the scanner and it read a voltage, so now I confused knowing the 5volt was signal wire not the zero volt wire as this had to be earth
@@ScannerDanner I'd like to subscribe too, I'd also like the book for the workshop as I do loads of research on RUclips then months later when I come to use it I can forget parts🤣 can we get the paperback copy in the UK
I have a small garage dont have enough faults or money to invest in wiring diagrams yet with all the other equipment iv had to buy, channels like yours are invaluable. Thanks.
@@chubbychequer1512 It would help me to know what you are working on. But if you added a load to the sensor ground circuit, this can cause the ECM to miscalculate the signal voltage as it is being compared to sensor ground. I'm really not 100% sure on that. If you were reading 5v on the signal circuit, the scan data should show 5v. Unless you are dealing with a variable frequency type MAF (like I am talking about in this video, GM in particular) and in that case they never report in voltage on the scan tool. Only in frequency
Every automotive repair course in tech school should require electrical / electronics theory. I mean in depth, not just basic "how to turn on your multi meter" stuff. It's disturbing how many "techs" out there have zero understanding of basic electricity.
Love this video Paul. Only if we could all download your brain knowlgade on to a driver and input it all and have 5000 Scanner Danner minds in the world woking on cars ha ha.
Every video I have seen on maf sensors all focus around P017 codes and don't get me wrong this video and many others have been highly educational but it still leaves me with codes P00BD & P00BF and closer to figuring out what the actual problem is
Define those codes for me. Also year, make, model and engine size helps me a ton!
@ScannerDanner my car is 2013 5.0L V8 supercharged jaguar xfr.
Dual intake both sensors are 4 wires
12v supply, IAT, signal and ground
P00BD & P00BF- Mass or Volume Air Flow A Circuit Range/Performance -Air Flow Too High
This is the information my service manual provides for those codes......
P00BD, P00BC, P00BF and P00BE As the engine uses two intakes, each with a separate mass airflow sensor and a single throttle, then
any of the air for each of the eight cylinders can pass through either of the throttles. This means that if there is a difference in air pressure
between the two intakes, then there will be a difference in air flow through each of the intakes. This is most likely to occur due to side winds
and in extreme cases can result in air flowing out through one of the intake ducts. The monitor is able to identify this flow imbalance
between the two sides of the intake system, so that the limits maybe adjusted in order to remove any tendency for false diagnosis of a
sensor.
Flow imbalance is determined by comparing each MAF sensor reading with the estimated value. If it is lower than a pre-determined
proportion of the estimated value, then the high fault threshold for the other MAF sensor is increased by an amount that depends on the
difference between the two MAF sensor readings. If it is higher than a pre-determined proportion of the estimated value, then the low fault
threshold for the other MAF sensor is decreased by an amount that depends on the difference between the two MAF sensor readings.
In cases of imbalance, both sensor readings move equally in opposite directions, the appropriate fault thresholds will be adjusted and no
false fault detection will occur. If a single sensor is faulty, then it can only alter a fault threshold for the opposing sensor, its monitor is
unaffected and will therefore flag a faul
@@ScannerDanner surely this hasn't stumped the infamous scanner Danner?
@@thomas_Customzcan't do this type of stuff through text on a screen. This is a complex issue and I have no silver bullets for you.
Post this to my forum (its free to join) and maybe we can help you there
www.scannerdanner.com
@ScannerDanner all good my friend was really just hoping this was something you have come across a time or two and could recall. I'll try out your forum and see if I can get lucky before I cave and just start buying and swapping out engine sensors and O2 sensors until one of them corrects it lol
How to join your students
You can join me here!www.scannerdanner.com/join-scannerdanner-premium.html
Thank you! Looking forward to hearing from you
Paul, i have a slow response from a new oxygen Sensor in a kia. Ill drive to south hills if you want want some side work and new content.
How can I test the g/s accuracy with MAF sensor? Does anyone know the formula or what is the test that gives the most accurate results?
the g/s accuracy at idle? Anything under a 3.0L, good luck. For g/s at wide open throttle/redline, the VE test is the way to go. You can use the calculated load data PID on global OBD2 mode too
hey friend I like to see your videos,, connect with you to know about the scanner
👍🏻👍🏻👍🏻🌷
temp and speed to determine density and the computer knows exactly the volume of cylinder too eh
Dam you are god
Just love this stuff is all 😉
@@ScannerDanner it shows through and we are so lucky to have someone with your passion.
Morning @ScannerDanner
Good stuff Professor.
So I commented on one of your other MAF videos and did not give all the specifics of my problem. I worked on a Ford Taurus with a clogged or contaminated MAF and it would not start. Before I did anything I opened the air cleaner and removed the nest that some chipmunks had built. In removing the air box I disconnected the MAF sensor and after I cleaned out the crap and reinstalled the air filter and the cover I was able to start the engine so I thought I had fixed the problem and was double checking my work and noticed that I had not reconnected the MAF sensor. After reconnecting the sensor the engine would not start so a little more looking and checking and pulling the MAF out of it's cover and saw that there was gooks in the wire. A little air blew the crap out of the wires and and I put it back together and it started up. All this to say that there must be a default setting that allows the engine to start if the MAF is disconnected at least on that year Ford. Okay That's all I got. Happy Motoring.
100% my friend and both GM and Ford have good backup strategies for the MAF (other manufacturers too, but not all of them)
THE BEST AUTOMOTIVE INSTRUCTOR ON THE PLANET ,,,,,,,,,,,,,,, IF YOU WANT YOUR KIDS TO LEARN FROM THE BEST THAN YOU NEED GO NO FURTHER .
Thank you!