How to identify and clean a dirty MAF sensor (Lexus)
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- Опубліковано 8 лют 2025
- A Lexus GS300 case study. (negative fuel trim numbers at idle and positive fuel trim numbers under load)
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.
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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!
Disclaimer:
Due to factors beyond the control of ScannerDanner LLC, it cannot guarantee against unauthorized modifications of this information, or improper use of this information. ScannerDanner LLC assumes no liability for property damage or injury incurred as a result of any of the information contained in this video. ScannerDanner LLC recommends safe practices when working with power tools, automotive lifts, lifting tools, jack stands, electrical equipment, blunt instruments, chemicals, lubricants, or any other tools or equipment seen or implied in this video. Due to factors beyond the control of ScannerDanner LLC, no information contained in this video shall create any express or implied warranty or guarantee of any particular result. Any injury, damage or loss that may result from improper use of these tools, equipment, or the information contained in this video is the sole responsibility of the user and not ScannerDanner LLC.
![MAF and Wideband O2 Sensor Testing for a P0172 [Rich Condition]](/img/n.gif)
Mr Danner You have kept your promise to provide content even after you started the premium channel. You are a good person and I respect you immensely .
+Tom A thanks Tom!
@@ScannerDanner 5yrs later after this comment and dude is still gaining all kinds of respect bc he dam sure got mine. Learned priceless info from u and its greatly appreciated.
What up SD? Anyone that finds SD's Videos boring is not putting their heart and soul to his work .All of his videos are fun and interesting... Thanks again SD...
This is best video about what dirty MAF sensor can do to a car and how to clean it PROPERLY.
I love how fuel trim data can point to fuel problems or air leak problems to do smoke pressure tests too. Such a cool and easy bit of knowledge every man / woman should know. They should add this knowledge to a driving theory test to help bring vehicle emissions down a little for the DIY people that would do it if they knew.
ScannerDanner, I can't thank you enough for this walkthrough!! I have an '01 GS300 for a few months now, and the performance/MPG has been dropping significantly. I logged into my OB2 Scanner today to look at some live stats, and saw a pending P0174 code (lean Bank 2). I followed your steps with some q-tips and MAF cleaner, and sure enough a dirty MAF was the problem! The ST & LT numbers I was getting after the cleaning were pretty much the same you saw after your cleaning.
No need to apologize for the intro or anything else, you the man. Thanks for your many video's you've been a lot of help to many. Thank you
Love watching you do your thing.. I am a mechanic, been a tech for a few short years.. But watching your video is a treat.. Is went to Lincoln tech, but did not get the inn dept lecture, the way you teach your students, it just shows me what I could've gotten.. Thank you for what you do ScannerDanner.. I've watched many vids that you have on your channel... Love it.. Your student should feel lucky..!
+Hiram Alicea thanks so much Hiram!
Can you do my maf sensor lol and clean my filter. Since your're in RI.
I watched one of your brothes video on maf sensors with same code and the next day i got an explorer with same problem. James danner video pointed at a low baro hz. My baro was at 130 hz and after cleaning the maf and driving for a day it recalculated the baro hz to 151.something to add to list of pids to check. Your brothers videos are great too.
After watching this video, I cleaned one blackened MAF thermistor, or whatever they call them. It fixed like 4 problems. Before that, the idle was a shred too high at times, it would spark knock just as it fired up, it would spark knock when accelerating, and excessive exhaust odor was noticable when idling in park. The spark knock problems developed more recently. Carb cleaner and a Q-tip fixed all of those things right up..
John Doe you're not supposed to touch any part of the sensor aside from the plastic. Touching the metal wiring with a q tip could damage it
Jack Tran did you not just watch this video?
Thanks, Dan I first cleaned the MAF sensor the so-called proper way then hours of testing and repairing and replacing plugs, coils, fuel filter, injectors etc my 2002 Jag XK8 with 170k miles on her and it still ran like crap. Then I found this video, WOW it worked! The old Jag is running great now. And to think it only cost me $5 for the brake clean to fix it. Thanks again. Cheers to you and all your $$$$ saving videos.
Great fix. Money in the bank. You are so right about it not always getting paid for what you, it's also what you know. Someone could go chasing a fuel pressure problem for hours and ring up a big charge for the customer. If I had to guess on the battery drain, it'd be whatever's connected to that big stereo cable!
Great job SD! That is exactly how almost every tech at every Toyota/Lexus dealership I have ever worked at cleans the MAF. It works! Sometimes just spraying it with that MAF cleaner will not get the wire completely clean and the car will come back.
Hi SD. I watched a lot of your videos which helped me to fix my Lincoln Town Car repair issues. I used CRC. MAF sensor cleaner and never used brake cleaner which is oily and neither any sharp object to clean it, because the sensor is too sensitive and would break very easily . Why somebody take a risk against $8.00 only.! Thanks.
You should definitely say "whaddup". I'm starting to realize that the more personality in a UA-camr, the more I like them. There is this guy called the SamuraiCarpenter and he's got a lot of swagger to how he talks, lol.
This not only helped me fix my IS300 but I also learned allot about fuel trim levels thank you !!!!❤
Your video was really helpful. I'm not a mechanic but after watching this I'm going to be cleaning the Mass Air Flow sensor which it's dirty according to the Diagnostic I just recently got and of course I'll be first removing the negative terminal of battery. Thank you SD.
Thank you!
ScannerDanner you didn't use MAF CLEANER, why?
Thanks man you fixed my car
The symptoms were hesitation/lack of performance with moderate acceleration up a hill
The mechanic put in a new fuel pump, some leads, a exhaust gasket,
I renewed the distributor cap, rotor and injectors ( i am new to fuel injection, always had carbed cars)
After seeing this video i cleaned the MAF with a cap of methylated spirits and a small brush ( a one cent job ) 1995 isuzu pickup
Now it gos like a jet
Thanks for you video and time
Awesome! Thanks for sharing
My car is really struggling up a hill. I hope its just a dirty mass air sensor
All these parts when it was just a dirty MAF or you were doing a major service anyway?..bcos those parts are costly even if they are not OEM parts!
Thanks for the vid. I'm beginning to understand long/short trims. Watching field work is definitely more entertaining. Keep it up man.
Just confirmed whats was going on with the BMW 530I in the shop,the car came in with an air leak, intake was torn, disa valve was leaking, i also replaced the pcv control valve. Fuel trim now is minus at idle which indicates to me there's no vacuum leak anymore, as soon as i start driving , fuel trim bcomes excessively positive.By the way I contacted you two days agoon your site about the ebook code , reply was fast, thx Danner.
Pocket screwdriver and brake cleaner, this is exactly how I'm cleaning MAF sensors. The only thing I would add, while doing this procedure, do not soak the o-ring with brake cleaner it will expand.
Good video Paul, understanding fuel trims makes life so much easier.
I just had an experienced with a failing MAF that was interesting. (3 wire analog Hitachi MAF in a '99 Nissan.) I had fuel trims that were high at idle (well over 20%), improving as the throttle opened. First hypothesis is a vacuum leak - but testing shows no leak. Also no evidence for fuel delivery problems. Fuel pressure, injectors, O2 sensors, etc all check out fine. I cleaned the MAF - with CRC spray stuff - no screwdriver! - no change. Also, using a DVOM, MAF voltage measured within factory specs at idle, 2500 rpm, 4000 rpm. The MAF also passed the test from your book: over 4 volts at WOT under load. No problem with harness, connectors, grounds, etc. The only clue was what I found with the scan tool: Even though idle was stable, the reported MAF grams/second reading at idle was varying by a lot: from 2.8 g/s to above 4.0 g/s. Why such a large swing when idle RPM isn't changing? Also, there was an inverse correlation between MAF output and fuel trim: Idle fuel trim was highest when MAF reported g/s was lowest. Replacing the MAF fixed the problem. The MAF was underreporting air flow at idle, but did better at throttle positions above idle.
David UM1996 crazy. awesome detective work my friend.
5:30 Negative ltft at idle and positive at higher rpm - classic dirty maf symptom. Thanks will try!
F'kin awesome. Been watching your videos since buying an obd2 and haven't been disappointed once. Keep up the good work
Thank you!
Good video and well informed. MAFS are different. Some have huge wires to the resistivity sensors and some have angel hair. If your stuck on the road with a spitting and sputtering engine and need help fast, this video can be a life saver. Take it from there and use some common sense. Of course using the proper air filter and changing it regularly can avoid most of theses problems.
Awesome video - I'm about to use Seafoam Spray for the top engine and wanted to see what else I should be inspecting. I'll take a look at my MAF as well! Thanks!
It also helped the idle, it was idling before the cleaning at around 550. After the cleaning it went up within spec at 700
I’ve cleaned so many MAFs on Toyota products and fixed them right up. I’d always start there. Takes nothing to clean them up.
For some reason.. (I’m guessing crappy paper filtration) they tend to dirty up real easy. It really is the first thing I check on Toyota’s for rough running and rich/lean conditions.
I think a, What's good with it man. Scanner Dinner here... is a nice manly intro. not for everyone mind but a suggestion none the less.. Nice video uploaded. Thankyou bruh.
I have ready that some MAF's have a coating that carburetor cleaner can damage. Brake Cleaner is certainly less powerful. Thoughts? Love your videos and your book. I regularly refer to it!
I think its well worth it and the coolest thing to be a part of, thanks Paul.
hi i live in the bahamas and ihave learn alot from your site and i just want to say thanks
i like the way you express youe knowledge...especially when yoy solve the problem..great to watch. i wished i was a car mechanic.
+farouk abdi you can be one if you keep following me. Seriously, I can make you a diagnostic tech
+ScannerDanner brother enough respect to you...i though you were just a good mechanic but know you have shown me that you are a good man.....a lot of people hide what they can do best but you what you know you teach to others...i promise you i will follow you not only you are a great mechanic but because because you are layal to your job by teaching others...great stuff.
+farouk abdi awesome, may God bless your path my friend
+ScannerDanner you gave me the best prayer...may God bless you 2....
may i ask you something...
i have a zafira Vauxhall, i did take out the air mass flow sensor cleaned it, to be honest the resistors looked very clean already I put it back on still the same..
symptoms:
when started cold, it sounds like back firing unstable noises as if it wants to stop. after 3 minutes it becomes normal runing smooth.
when the car is worm it seems ok...but the problem is gettting worse as days goes.
another clue when i start the car while unstable the accelerator does not respond bo matter how much i give it gas????! after 3 minutes it becomes ok...
honestly i dont want to disturb you and take your valuable time. i welcome any directions from you.
Thanks for the info Dan! Helped me makes sense of all my scanner data!
This was a nice typical case solved by fuel trims. I will try next time during my diagnostics.
Thank you so much for what you do your credit to your profession I'm so glad I took the time to spend with you it's been invaluable.
Your videos on scanner readings are great. Thanks for sharing.
In the UK for my 2002 Yaris the MAF costs £ 138.99 WFF!! Just for that little thing.Good video by the way.
Please! There trying to make pocket screwdrivers illegal! There very dangerous Paul! Have you been properly trained?? lol, it’s just like the other day I was sitting next to you at the ASA Big Event 2019! Hope I get to see you again! You are awesome Paul! I appreciate all your hard work making these videos with your son! I’ve learned so much!! ❤
Dear sir ur honestly awesome i learning day by day ! Ur genies ! Best ever
SUBSTANTIAL Sir ScannerDanner
Tutorial great thank you very much.
Sir ScannerDanner
From Nick Ayivor from London England UK
Thanks Danner for yet another great video, nobody cares how you sign on just care about awesome information. Keep up the good work.
What up Danner! Thanks for all the amazing info and instruction. You are the reason I got into diagnostics.
What up Seth! Haha
Seth Harrison 😂
Ive always cleaned my MAF with carb cleaner and it always works fine.
Well I need this guy to do all my repair videos. I like this guy lol
I love your field work!
I almost thought you had forgot about us non premium subscribers :)
Great job & commentary, ScannerDanner!
good jog broth i verly finish the videon on primium channel for maf sensor n i understand the video well im just a student n one day i will be a tech like u 👊 eve tho i dont speak english well but i still learning from u great tech im from long beach CA
Great explanation for finding the MAF fault and how to clean it, thanks. Have issues with my Zafira. Used a bluetooth plugin adapter to connect to my android phone/tablet and it keeps coming up, a couple of times a week, with MAF fault and fuel trim. Hopefully save myself a bit of money cleaning it. Let you know the results.
+LordBazilBarrington don't forget a vacuum leak can set MAF and lean exhaust codes
+ScannerDanner Thanks I did watch another of your videos showing the smoke machine to find the leaks too. Shame I don't have the equipment to do that. Could try a disco smoke machine I suppose. LOL!
I use a vape to check for the vacuum leaks ha
thank you for this excellent explanation
Manners manners and man you’re the man you’re right
I replaced mine recently on an impala I had rough idle,when I put my foot on the gas rpms would go to 0 and it would try and stall, and one time I was driving it to get the part pushed in the gas and no response replaced the 166 dollar piece of junk and now it runs fine
I just bought CRC MAF CLEANER AND THROTTLE BODY CLEANER. THERE IS NO INDICATION OF ANY FUEL ISSUES WITH. MY 2003 SATURN ION. IT STILL PURRS LIKE A KITTEN, BUT I CONSIDER CLEANING THESE PARTS AS GENERAL MAINTENANCE.
I HAVE 169 THOUSAND MILES ON IT. BUT, IM STILL CONCERNED WITH MY '86 , 302, F150 AND MY BROTHER'S 99 Toyato Camray Solerno.
TBH I've used brake cleaner to clean MAF & MAP sensors. I checked it didn't leave a residue once dry, installed, car runs fine, no problems. Good thing about brake cleaner is it really cleans the oil and carbon good.
with 170k on my toyota echo I finally replaced the MAF sensor and corrected the P0171 code lean run error. no amount of cleaning would fix the original sensor. it lasted a long time. now the replacement was 19 bucks and it corrected all the problems. price coming down on MAF sensors for older car. looking at the original sensor its clean but just does not work properly anymore.
Your the man brother. You help a lot
+mark ortiz thanks bro
Thx Scanner Dan for allowing me in to your class. I learned a lot, but my 07 Jetta has me baffled.
It ran great when I bout it, super fast.
Had battery issues, and it got ark like twice.
Check engine light came on. Code said maf sensor. Put a new one on. Trunk light came on, wouldn't pop open, hand to go thru the trunk. A/C stop working. Then the ESP light came on. Then it went into Limp mode. Now it will crank no start.... Then I disconnect the Maf, and it ran...but still in limp mode.
I'm just throwing parts at now???
Do I have to take it to the shop. 😢
I to shaky to try cleaning one like that . Good job.
I use mass air flow cleaner to do my 2000 toyota echo maf. I am going to take a much closer look to see if I am getting the crud off the resistors.
Yay, thank man! After cleaned it, engine idle and run so smooth. 👍
Great informative video Paul, thanks for sharing
Good morning scanner Danner I am a technician in New York and I was wondering how do you go about invoicing customers for a dirty MAF sensor, what do you include on the Bill? do you include scan data or screenshot of the scan data?. I ask because sometimes I find myself in a situation where the customers find it outrageous that I am charging them just for cleaning apart most of the time I feel like they would have preferred if I would have replaced expensive part then just clean it
Regarding and idea for an intro, how about a rock music riff and countdown (1...2...3...4) and then you cut to a burnout of a motorcycle wheel?
Schrodingers Box hahahaha
Schrodingers Box wait, isn't that scotty kilmers intro??? I'll pass
ScannerDanner
ScannerDanner Do what you do. I am perfectly fine with your intro. I feel very blessed to have found your channel. Your have inspired me to become an automotive diagnostician. Thank you very much Paul for your contribution to the automotive world for aspiring technicians as myself and others.
ScannerDanner But you could make it look cool, With Scotty it's just...annoying. Or you could use an Aussie accent, move your hands a lot, and emphasize each word like an exited 4 year old. No, wait.. that's kinda like Scotty, too.
"Hey guys" is fine.
Congrulations from turkey;big master
I like your style big master
Thank you for taking the time 🙏
youre awesome dude! keep up the good attidude
Great video,thanks for passing up your knowledge,.im learning a lot with your videos,
Thank you for the content. Did you ever find out what was causing the battery drain? I have a 2001 ES300 with that issue, still trying to figure out what's causing it. I think it may be the auto headlights.
Hi bro i am watching you From Bangladesh
Welcome!
That Airman is crazy, but anyways, beginning to understand some on LTST reading etc... makes its lots of fun once u get a better understanding reading the scanners correctly, thanks for giving us the auto enthousiast some great tips etc....
+hunkydude322 thanks man
You have to be super careful if you try to scrape the resistor elements clean..those wires are hair-thin. I would have started with the brake cleaner first,less risk of breaking the tiny wires. Good fix.
I’ve had a low idle for years. Can’t fix it. Stuck at 400 rpm.
Replace maf
Replace throttle body and the metal piece attached.
Found 3 cracked pieces replaced them all. (Over 3 years)
Tried the turning the key back and forth trick.
show, I have done it many times on Ford MAF sensors and saved it
What do u charge for a job like that in the field? Great simple video really helps to understand. Thanks. Will be taking your whole pay course soon!
hi there
i have no word for your good videos on youtube . just love them . God belles you for your good work. can you pls tell me where to get the test lead you use, and what model it is .thank in advance.
afi 121 thanks man! it's an old school Snap-on Mt2400 Vantage. The test leads are from my Verus
Looks like someone installed and oiled K&N air filter in that GS that coated the MAF sensor. I would not recommend an oiled air filter in a MAF configured system.
I’m glad I didn’t go with the K & N on my GS350! I read somewhere that it lets more contaminants in so I went with OEM engine air filter from Lexus dealer.
I’m a little confused on the negative trim with a dirty MAF. Just trying to learn this but that got me.
Only at idle. You'll still have lean conditions all other times.
The best description that I've ever heard as far as this condition goes is at times of low air flow rates and larger surface area of the mass air flow due to the contaminants it actually dissipates more heat hence the rich condition
@@ScannerDanner Thank you for answering. I was approaching this under the premise that the contaminants on the MAF acted as an insulator thus falsely lowering the amount of voltage required to maintain constant MAF temperature under all conditions.
Dan information is crucial in diagnosis, Shop Key requires a business license which most techs don't have, where is a good place for the technician to get information from when doing side work at home without it costing $169.99 a month? Wiring diagrams are so important when troubleshooting.
try spraying a q- tip with cleaner,to clean sensor, works well .
Thanks for all the great info Mr. D! but would graphing the maf gps also have told you anything ?
sure, I have videos on using MAF gps on before an after cleans. Also for VE testing
@@ScannerDanner thanks for replying, i saw that and about 50-60 of your videos since my comment. Now watching classes and following with the book.
@@michaelmenard8913 awesome! Thank you Michael
Thanks for showing me how to clean that out she was dirty
6times out of ten i use brake clean but even tho you clean a mass airflow doesnt mean its good thats a temperarely fix. There is a 5v snap throttle check and i bet you it wont pass. But good video,sometimes jobs have to get done fast. Keep up the good work.
thanks brother, this did the trick.
I literally stretched, meditated and listed to how to fix my Toyota echo all at the same time. X)
awsome post SCD....thnx...ill need to purchase ur material fo sure
Pocket screw driver the multi tool great video
Christopher Barone I know, I even eat my lunch with it sometimes :)
YOU ARE THE MAN
i have a 92 lexus sc300 5spd thats giving me a hard time Danner.. ive watched your videos and i think your great at what you do.
replaced the ign. coil, distributor (entire assembly), plugs replaced with same plat. spark pluggs it had for 114,000miles. car has 126,000 now and it starts and runs good until its up to temp and then its starts missing and cutting out when giving it a good bit of throttle. everything else is fine. No check engine light as its an OBD1. The Iacv was cleaned along with the throttle body (both were taken out of the vehicle to be thoroughly cleaned) and the car idled better and ran good.. for about 20 mins... now its doing what i told you- missing like terrible, wont stay running, have to stay on the gas or when it stalls give it a good bit of gas and she starts right back up.. i feel rly dumb as i always figure out whats wrong but im rly stumped on this one... PLEASE HELP!
you made no mention of testing fuel pressure. this would be your next step
that would be fantastic if you had video of chasing that battery drain or if there was one instead of a bad battery. Does pete not do electrical work himself just curious.
Just did this yesterday on a 2000 Lumina, brake clean for the win, never had an issue with it. Don't have the balls to try and scrape it though. =P
Trying to help my son had same issue changed out mass air flow throttle position sensor valve cover gaskets vacuums lines look a little cracked and still starts up revs high then dies … o2 sensors both been changed and yet not sure if he has a vacuums leak or even hooked it back up right !! Plz help buddy 🤒😵💫😵💫
Thanks alot bro my problem is hopefully solved 👍
Wow what a difference.
wow! you are great. Great vid. easy to understand even for a novice like me. You skipped all the BS and focused on the important information. nice
+kk84 kk84 thanks so much!
good info . checking on why i cant get my dash guages to come back on.
Just wondering, It looks like that pocket screwdriver has a magnet on the butt end, shouldn't we be concerned with it around an electronic part? Thanks
Wasnt you suppose to disconnect then reconnect the battery for the Ecu can recognize the clean maf to updated specs?
It will learn on its own
ScannerDanner. Not vehicle related. Where are you located? My last name is Danner. I was born and raised in Southeast Alabama. Just curious. Although I did find your UA-cam video while looking for a check engine light. Code told me to change MAF sensor. I like your site. Thanks.
Pittsburgh PA my friend. Always great to hear from another Danner!
HI Paul ,you are the MAN,but you know it.I have an old 85 Vette,this is a one year car since GM went with bigger modifications since the next MY.The car was garaged in the last 2 years and when i recently fired it up i obviously had a rough idle,engine stumbling and a nice SES steady on display...I know that f...g rough idle and i was expecting some 33 or 36 code all MAF rerlated...it was the case...long story short my 33 code indicating a maf sensor high reading vs tps was stored in memory.My first check was if it was the MAF the culprit,or the pricey MAF module by bosh rated at about 250 $ and ...discontinued.BTW the MAF is a 400 bucks item not better...MAf was ok since it hadn't 12 v...i jumped 12 v directly from the battery to the 12 pin of MAF and SES went out...It was the module,next check was assure if it was a faulty module or a wiring issue, or simply an oxidized relais coil lead...it was just a couple taps on the cover (after dismantling an entire dash to reach the module...problem solved...
good content and good material I like the quality of the videos I want to start recording videos , may I ask you what is your set up what type of camera do you have ?? thanks paul
What is a good number to use when looking at fuel trim........just gat into the field my instructor told me plus or minus 10 because 20 is to high of a number and he showed the class how some people in the industry use plus oar minus 20