How to Test a MAF or MAP Sensor With a Multimeter - Plus an Operations Guide

[@NZbluesky]

8 YEARS AGO! You sir, are a shining light to people like myself! An old electro mechanical engineer... 2 million views? Fabulous teaching! Greetings from NZ

[@yannickkay5099]

After years your videos still educational videos you teach me easy tricks to test a sensor without wiring diagram that's amazing bro... Thanks sooooo much

[@TheRichardmay1]

By far you are the best channel for learning auto systems. your explanations are simple and clear. thank you so much. also great sense of humour every so often.

[@luisaliceaortiz7791]

Richard May thank you for time and efforts I'm always wanting to learn more .stay blessed

[@darrylkishii9359]

Richard May Q

[@donaldhollums3278]

I'm a long time, automotive DIYer and am getting into doing light automotive repair and service side work. I'be watched a few of your films along with DIY Auto Tech and Scanner Danner to help me improve my diagnostic skills instead of just being a parts changer. You have another subscriber, Amigo. Keep up the great work!

[@andrewngwenya6837]

This video has actually taught me how to distinguish a MAP from a MAF. Many thanks for the lecture.

[@politicalfoolsandhorses]

So very well explained. Really good. But please note that that MAP sensor is good. It increases the voltage only during acceleration. So if you are doing constant 20MPH it will be 1/1.5 depending on car make - it will go us as son as you decide to go from 30 to 60 and will stay up untill you reach 60 and release the pedal slightly (vacum if you have a vacum meter - many call it economy metres - goes down and Absolulte Pressure returns to normal) and the fuel mixture changes to lean again. At 60 MPH it changes according to the reading of the MAS Airflow Sensor. Anyway - the industry needs more people like you Well done again.

[@arniet1]

Thanks for that info. Is there anything simple that can cause a map sensor fault that can be easily checked without buying a new map?

[@politicalfoolsandhorses]

I am not sure I understand your question. 1. Anything simple that can cause a map sensor fault is. The map sensor is located in the inlet manifold after the air filter - it can get dirty / contaminated especially if you remove the air filter and use a gause filter or a filter which is not so good at filtering the air. Very easy to remove and clean. Many videos on U tube - only one screw maximum 2. It is vey reliable but its an electronic part and does not really like engine vibraions - and the engine heat. So it depends which car. On my car it has 153 K miles and never chaned. On my wife car it was changed after 163 K miles. 2. fault that can be easily checked without buying a new map? I would say that anyone that wants to test the electrinc sensors of his car himself, apart from the fact that deciding which sensor, if any, is the core of any issue to sart with; he should buy a Code Reader also called a Scan tool since it scans/checks all the sensor. Thanks to mass prodyctin these are ridiculously cheap - 24 Dollars sometimes even less from the shop than from Amazon. Googel - "car cheap code readers" or Go here: www.google.com/search?q=cheap+engine+code+tester&oq=cheap+engine+code+tester+&gs_lcrp=EgZjaHJvbWUyBggAEEUYOdIBCTIxMDM5ajBqN6gCALACAA&sourceid=chrome&ie=UTF-8 i@@arniet1

[@StormFlinix]

Been watching your vids for years. You know they're good when I come back and refer to them while on my projects

[@davidboles9166]

Great job man! I have searched many videos on various car repairs .You have covered 3 of the problems I have had. You rock bro!!

[@richardwallinger1683]

You are definitely the man . at 72 years young I understood everything you were testing .. My VW 2.5 TDI 2001 199,000 miles has gradually lost pulling power .I replaced the old original exhaust with a nice new Stainless de cat system .It was marginally more responsive , but after fitting a pressure gauge to the intercooler housing the measured boost topped out at 11 psi. I was told to expect up to 18psi. The MAF sensor was replaced for testing only and the difference was unbelievable the turbo boost increased as before but then continued to increase easily passing the 1 bar pressure gauge I had plumbed in . now all I need to do is attempt to clean the original MAF sensor and see if it was recoverable . my short journey transport is a 2011 Nissan LEAF . Everyone should have one of those .. they are the future.

[@jamesjohnson5700]

Can car have both map & maf?

[@dondale68]

I do like your videos. Myself, I find some of them boring but I've been working on cars for over 30yrs, but for a novice these are great! Not too much technical detail for them to lose interest, just enough to keep their attention and teach them how to fix their vehicle!

[@vladimirpetrov9717]

The map sensor is fine, when you crack the throttle slowly, the engine spins up, but the throttle does not open further. That causes more vacuum to form inside the intake, typically the map will read about the same as at idle or lower (since the pressure is usually lower). Otherwise cool video!

[@Puppunanne]

petrol engine , normal ....

[@jamesjohnson5700]

Can car have both map & maf?

[@TheWindrunner88]

@@jamesjohnson5700 yes

[@jamesjohnson5700]

@TheWindrunner88 ok because I can't tell if my 2019 Hyundai Elantra se has one as in maf

[@TheWindrunner88]

@@jamesjohnson5700 I’m not sure about those, might be able to google it tho

[@AmharicMusicLyricsVideo]

you are a good mechanic u explain with the mechanism how it works also the volt resistance testing failure solution amazing

[@jettpatton4618]

Hey bud I really liked the way you translated this,you made it very understandable because you know your shit. Thanks bud for taking time to share.

[@W.Khairi]

Regarding car repair this is one of the best watched so far......its a truly door opener.....Thank u very much

[@ashishacharjee8018]

U r really good.....I just saw another video by an automotive engineer. Combined with ur video, everything fell easily in place. The engineering info with a knowledgeable technician’s experience.....is the best tutorial.....thanks

[@WmTyndale]

Another beautiful explanation. Especially that the IAT sensor is in the MAF in the newer cars. I like your deep knowledge and precise explanations. RECOMMENDED!

[@uguraker8930]

Bravo ; for 1-fluent spoke 2- fully own and controlling science of this subject. 3- loving your jobs 4- your teaching talent(gifted , from God)

[@froglegs4910]

I LOVE YOUR AUTO REPAIR LECTURE ! VERY CLEAR EXPLANATION AND TRUELY PRACTICAL ! THANKS LOT FOR YOUR UPLOAD VIDEO !

[@boybravo689]

Sir tnx for showing us how to test a sensor using a voltmeter most of us newbie mechanic can't afford to buy a high end instrument tnx for all the info sir subcriber from the Philippines

[@osvaldoumana4494]

super clear.... great video.... thanks a lot!!!! i just got my new OBDII scanner and with this video I hope I can fix my kids car.... next...THE WORLD!!!!!!

[@Johnsmith-zi9pu]

To reduce vacuum you have to apply load or disconnect the vacuum tube. That sensor appears to to be working OK.

[@tomreyn3610]

Yea. He is wrong about the MAP. Bad test. Quick rev response was correct. He interpreted in wrong. MAP was good.

[@uphill248]

Can a car have MAF, MAP and IAT? Also can you use the same cleaner for all of them?

[@Rabbit.760]

Wow you teach better than anybody I know of. So well, that your accent sounds fluent

[@bilalcassim4509]

one of the best mechanics on youtube keep up the goodwork , good videos and always spot on . helps me 100% of the time

[@muriuwangai3617]

Awesome. Kindly advise me on what tests to carry out on my g16a sidekick engine include TPS, etc

[@davidsibble7429]

Very very good video..appreciate the attention to theory as well as active repair. Shows true reinforcement to problem solving 👍🏼🙌🏼😎

[@politicalfoolsandhorses]

There is one think I need add for the less knowledgeable/experienced. Identify the fixed supply voltage first using Volts setting. No damage can be done while testing any pin for volts. HOWEVER ONCE YOU CHANGE TO OHMS, to identify the ground wire, you MUST make sure that you NEVER touch the Supply Voltage Pins again. Under OHMS , the meter will short the supply voltage to earth, blow a fuse which might not blow fast enough and you could cause damage to the electronics, So be warned. You either do it in full conformance with how this man described it or you could do more harm than good.

[@RoadRunnerMeep]

Great video, very detailed. What were you using to test for a vacuum leak from the N75 valve when you determined there was no leaks. What should have happened if there was?

[@wyattoneable]

I missed the cut off but I really have no questions. You do a great job at explaining the components and circuitry so it's just a matter of getting out there and experimenting for myself. Thanks.

[@Chris-hx3om]

No he didn't. He doesn't understand the difference between a 2-wire and a 3-wire sensor.

[@bluor3713]

@@Chris-hx3om what's the difference between a 2-wire vrs 3-wire?

[@Chris-hx3om]

@@bluor3713 2-wire is a resistor and the ECM is looking at the current flowing, whereas a 3-wire is a voltage divider where the ECM is looking at the voltage between two power rails. The advantage of the 2-wire is cost, but at the expense of repeatability with varying voltage rails. (Automotive is notorious for quite a range of voltages. Less than 10 under high load without the engine running, to over 14v once the battery is fully charged.)

[@slimeroad]

Very practical video for determining baseline characteristics for each of these devices. Thanks very much from the UK.

[@bentonklock903]

RnW, Big question for ya. I need some help from you or the group. I am working on a 2003 Audi TT quattro. She threw a handful of codes that lead me to believe that there is one (maybe 2) sources causing the codes versus 5 to 6 actual failed components. The codes are; P0031, P0037, and P0141 all pertaining to Oxygen sensor heaters. I tested the sensors and they tested good and in fact are not getting 12v from the ECU. THe next series of codes are P0445, P0449 and P2401 all pertaining to the EVAP system valves and leak detection pump, I have not tested any of these yet. There is a P0414 and P0418 for the AIR system switching and control, the blower is working properly, I have not yet checked what the voltage is that it is receiving yet. The one that I am hovering around is the P0102 Mass air flow sensor "A" circuit low. All of the codes are referring to either a short or low circuit, when I tested the MAF sensor the voltage with the ignition off was sitting at 1.49vdc and when started it was all over the place and never settled anywhere and would dip as low as .004 vdc and barely make it over 1.0vdc. I think I gave as much info as I can at the moment. Let me know what I should do from here so I don't start throwing parts at it.

[@bentonklock903]

After many, many hours/days/weekends of troubleshooting this problem I found the source. Fuse #43, marked "engine,petrol". It is hard to admit to such a simple fix for this but that was it. I noted that all of the failed components (indicated by trouble codes) all had a common wire "blue w/ yellow stripe", traced them on the schematic and shot it back to the relay, then the fuse.

[@niranjanomram271]

big question for you. I need some help from you my vehicle start ok but when u attempts to accelerate it cuts off, I try to start it again it start and when I try to accelerate it cut off, it keeps going like that all the time

[@daboys66]

Excellent video and demonstration!Do you have a video for checking vacuum leaks i have a 94 ford f150 5.0 XLT

[@lorchri14]

Working on Onan generator, EFI, so so helpful to understand these sensors and how to test. The manuals only give resistance parameters out of box, not operational.

[@OverturecervejariaBr]

Very good video. This is the right way to diagnose the fuel injection system.

[@wrapcityhqvicmelbourneaust6570]

My map sensor went bad and I thought it was the map sensor I just replaced it for ten bux brand-new. Instead of doing all the checking I'm just saying if you want to learn it this is a great channel I like it a lot

[@guysmith6616]

Thank you. Could you please say what you spray the hoses with to check for leaks?

[@billyburns3792]

The reason the voltage didn’t go up when you opened the throttle slowly is because you didn’t lose vacuum until you opened the throttle wider

[@lorchri14]

Forgot to add, thank you for getting to the point and not making me filter out off tangent superfluous crap.

[@christen1075]

Step 1. Locate MAP sensor location on your car. Step 2. Reconnect electrical connector to said sensor which had failen off due to the little hooter that holds it in place being broken. Step 3, employ white zip tie to prevent this from happening again, inadvertently. Step 4. Leave nice comment about well taught lessons on MAP and MAF sensors to RnW big guy. Step 5. gloat to your kids how you're now an ace diagnostician. Step 6 sheepishly thank the Lord and RnW for making you learn something without buying a part willy-nilly.

[@bpdp379]

I’m on step 4 currently

[@prashannabalaji8532]

In case of MAF sensor, will current be left constant so only the voltage varies with respect to resistance of the hot wire?

[@toomuchtruth]

This is exactly the video I need right now as I try to fix my car. Almost like if you made it just for me, lol! Thanks a ton for this!

[@myRatchets]

lol nice, glad its useful to you. cheers

[@thecrittergitter7576]

What are you using for testing for a vacuum leak? Vacuum won't bubble up under negative pressure.

[@gasgas2689]

I love this. I must learn more. I have been fixing cars for 50 years, but always the older non-computerised cars. Now I have spent a thousand $ on incompetent garages using their computer diagnostics and believing the computer instead of using the very few brain cells the Lord God gave them. From now on I will watch and learn from you.

[@juanorte3526]

Thanks! for this video, easy to understand man. I said hi from Uruapan Michoacán México 👍

[@Jan_Seidel]

Cheers. Learned a lot new MAF in 2 minutes!

[@IrfanTahir]

your explanation is very precise and simple as well. Great job and thanks

[@samer4977]

now i understand the maf sensor but i have one question is if the pcm give that maf sensor 5 volt to function it and the sensor it self resend voltage to the pcm by ground wire ( what the function of 12 volt wire?? ) sorry for that question but im still beginner and English is not my native language

[@devsamEXPOSED]

Your MAP sensor was just fine. It measures PRESSURE, not volume. When you open a throttle slowly you barely increasing any pressure but you are increasing the volume which is why it was properly working the way it should.

[@myRatchets]

you might be correct sir, gona have to bench test that thing. will update results.

[@valentinegutierrez3905]

Dev Sam b

[@michelguevara151]

he obviously thinks they're the same thing. bit of a jonny-know-all-wanker.

[@andrinirainyramanantoanari8162]

@@myRatchets So, in the end what was the problem?

[@33798]

Very good explanation of MAP and MAF

[@observersnt]

Thank you for your clear, simple and methodical approach and for the time and effort you have put into these videos. Please forgive my ignorance, I am, as you will see from this question, still learning: If in the course of probing or back probing to identify wires in any connector, I connect my multi meter with its 9 volt battery to any five volt signal wire, is there not a danger that I may damage or destroy the five volt signal generator(?) or regulator in the ECU?

[@stevejohnson8773]

No. The meter is designed so as not to damage the circuitry it is testing.

[@chriscrystalhood6260]

what were u spaying to check for vacuum leaks, does it suck in what your spraying,is that how you know there is a leak.

[@jmerrow02]

I have a question I have a gmc 5.7 1998 3 wire on mass flow 1 is 5 volts the other 2 go to ground what would be you best thought also when I disconnect mass flow when running nothing happens bod reader says bad mass flow and bad cam sensor I installed new distributor with cam sensor no change aks changed crank sender. Thanks Something else truck keeps fouling 02senser upstream bank 1

[@dustindykman2380]

On GM Map sensors they will always read 5v from the power wire, so that's nothing. And you unplugged the maf and the ecu didn't respond? Sounds like a red flag to me haha.

[@jmerrow02]

Dustin Dykman my hole problem was a bad fuse connection took a week to find it

[@alextorreblanca8589]

In the case of a turbo application like the 2004 Audi A4 1.8T when the BOV (in recirculating mode) relief boost pressure back in to the intake, wouldn't the MAF experience flow in the opposite direction?

[@Robbie-Robb]

Hi. Great video! Question? How do I test the MAF and IAP sensor if my car is in limp mode???

[@michaelmorgan5714]

What were you spraying on the vacuum line to test for a leak and how exactly could you tell that there was a leak. Thanks Mike from Maryland

[@satanme1709]

Starter fluid..if there's a leak vacuum will draw it into the engine and cause the engine to surge/accelerate

[@tiaanvandenberg5328]

Will a dirty MAF sensor have an effect on idling and random engine stalling. I get this issue about every 12 to 18months?

[@tiaanvandenberg5328]

Finally resolved the issue. . Did a diagnostics test. It indicated some issue at the throttle body. Strip and cleaned it. Put it back. Problem fixed right away. I was told if it happens again within a week or 2 i need to replace it. Luckily its cheap.

[@AnjouBlaxx]

What was the year Mike and model?

[@amogarage]

Great video, helped me successfully diagnose a faulty Map sensor, thanks a million

[@Purosanluispotosi]

So how u know wen that sensor are bad that numbers stay on place or wen go up

[@ex8280]

Dang 2 Million DiY'ers was helped by this video. Congrats.

[@jimnolan8207]

Two questions, what were you spraying to check for the vacuums leak and is there any danger with testing for ohms and you hit the power supply wire?

[@myRatchets]

I use brakeleen, starter fluid (could start a fire) safe way is to use propane. I have a video on finding vacuum leaks. Yes, don't check a hot wire for resistance you can damage your multimeter and or the wire. Thats why I checked for power first than excluded that wire/pin for the continuity to ground test. gl

[@spike121964]

Love all your videos. Great work

[@51exequiel]

Is there away to repair MAF sensor first before buying a new one like cleaning it first ?

[@Buckwsr]

Great video! What were you using (an aerosol can) to test the vacuum line for leaks? Thanks.

[@myRatchets]

starter fluid, be careful as that can catch on fire. Propane is safer.

[@michaelking42]

Great, great video, thank you for taking the time and effort to make it.

[@fabiobatalhadesa1586]

Hello... I'm Brazilian, see your vídeo very good... congratulation!!

[@LukeSchiralli]

Great video, very informative and easy to follow thanks!

[@TomO-if7nh]

Will a dirty Mass Air Flow Sensor make the car stall? Also, on my car when I unplugged the MAF, my car shut off. My brother's car is stalling when driving, when I unplugged his MAF, his car still ran. Any ideas? Thanks

[@turnupdot2108]

Tom O did you ever figure it out I’m wondering the same?

[@TheDangerzone94]

If somebody needs the information: it depends from car to car. Remeber: the maf or map sensor is used to calculate the air/fuel ratio. If you habe a broken, durty, ... sensor your engine can have trouble to calculate the right mixture. Old cars dont have as much problems because there tollerance is a lot higher. Like old and new diesel engines. In new cars the engines are so fuel efficient because they are tuned very well. But pefect tuned cars need more love. So some cars will go out, some will go into a emergency programm... it can depend hard. But yes it can make your car stall and stuff. Like in the video you see when he applies hard throttle the sensor "work", but when crussing it wont. With a maf sensor it can also be that you get some "wrong air" after the sensor (when you have a hole in your system where it sucks air into the system after it passes the maf sensor). So the sensor doesnt register all the air what is going into the engine and caluclate the wrong fuel air mixture.

[@kamcando]

Great video 👍🏽 what r u using to test for leak pls? The can says "START.." can not read the rest.

[@Rabbit.760]

Starting fluid probably

[@knight4plays]

2004 vw Jetta 2.0 sedan 1984 CC engine code 2177 lean bank 1 off idle I've changed everything emissions related can you walk me through all possible causes to compare and see if I missed anything. Thanx, for your help!

[@stephenarling1667]

This is great explanation, and much easier to remember after second viewing.

[@ricardoolguin9607]

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[@JohnR9965]

You do great easy to follow vids. Two thumbs up.

[@myRatchets]

ty ty

[@sungodapollo9093]

Thank you I am getting the MAP/MAF code issue so I have no idea what's the deal. The throttle does not seem to open up when I rev the engine. When I start my truck it cranks but turns right off abour 4 to 6 times. Sometimes I give it gas before I crank it and it works. 04 Colorado LS 3.5

[@sandygrungerson1177]

a graphing tool would show any irregularities in the voltage, which is useful for finding intermittent MAF problems

[@ScreenPrintR]

What is that spray you're using to look for a Vacuum Leak, around 5:49?

[@skywayb9]

I have a 1992 accord that vibrates at idle. I have replaced the IACV, EGR, spark plugs wires, new distributor, cap and rotor, motor mounts all 4 new, clutch damper, power steering pump, and rack, alternator, battery...everything! The tachometer is never bouncing and always very steady and right where it needs to be. I can't find any vacuum hose leaks. New fuel injectors, pressure regulator, air filter, fuel filter. I DO NOT have a check engine light. My question is this, can a faulty MAP sensor cause the engine to vibrate at idle and not throw any codes nor have an effect on the tachometer? Thanks, Billy

[@imagegraphics16]

Nice video thanks! my plug is reading 2 constant ground,(mass sensor) e250 2006' whats wrong?

[@veggie786]

I have a question, the ground wire on my map intermittently has no continuity, garage say the wires are all fine. But car occasionally goes to limp mode, could i test the ground by putting it on the engine or does it have to go to ecu ground all the time.

[@HomeMadeBoards]

Make sure your engine is grounded in a 'star grounding formation'

[@veggie786]

@@HomeMadeBoards i decided to make a new ground on the engine block with new wire. Has been working since..

[@javamochafrap]

after you check it what is it you are looking for? is one or the other one good or bad?

[@tokgaenz]

thanks you so much , all your video is easy to understand and educational

[@SpiritsOfWarding]

What did you spray on it to test for the vaccum leak?

[@Jpilgrim30]

An oscilloscope is about the only reliable way to test a mass airflow. I've seen MANY MAF sensors that looked fine on a scan tool and a multimeter that had tons of glitches when viewed on a scope. Glitches that were far too quick to even hope to see with a meter.

[@oscarronquillo7794]

well said...

[@JrSpitty]

If you wan't to be certain. But good oscilloscopes kind of cost a fortune in contrast to a cheap reliable multi-meter. They also require a lot more proper care.

[@samlloyd8668]

BUT... a cheap DMM will tell you if the sensor is bad. So, you have a point, but a meter isn't totally useless. BTW, What causes the spikes you mention? Is there active circuitry inside the sensor, or is the hot wire the only component? Just curious if the spikes are due to a compromised connection, in which case it might be easily repairable (solder joint issue?), or is the platinum wire welded, making it irreparable?

[@jasonmcnamara2079]

sometimes analogue meters are better than dmm's for this type of stuff

[@nealeng.1063]

Thanks for this very informative information. Great details !

[@ΝεραντζηςΝικος]

The voltage supply to the sensors is from the ecu or from the fuse box?

[@nosurrender7275]

Νεραντζης Νικος voltage comes from the battery and alternator initially the fuses are only to protect the wiring from overloading under a fault condition and melting...the sensors turn all information into electrical values in pulses or voltage then the computer is ablebto read that and makes adjustments as needed....as far as I know

[@mayamikokayesa171]

well done will get the ball rolling great show

[@samer4977]

idle control and map sensor and maf and iat sensor what the different and the relation between these sensor every one one you tube said they regulate air flow ( ineed more explanation ???

[@crank3646]

You forget to say few words about digital MAFs . Great informative video as usual !

[@myRatchets]

I did, it didn't make it past the editing room. good point.

[@draid9564]

I think I have this issue with MAP sensor connector wires. One of the wires was damaged and I had to splice another one in, so I think the connection is not that good causing readings and codes also making the fuel run lean, thanks for the video very helpful.

[@milesdavis7644]

the quickest way 2 check any sensor in your car at multiple working time is to start your car while the car is running..using a car computer set it on live data if it is avalible on the computer, it will tell you what ever u need 2 know about any sensor live and direct..

[@safebarbell]

Hi. Good video. I've checked the voltage at the plug from the loom. I've got 4.99V on one, 4.56 on another and zero on the last. Ignition on, engine not running. Is there his correct please? Cheers

[@politicalfoolsandhorses]

MAP sensor detects that driver pressed the pedal to accellerate. from 30 to 50 MPH. Input is always a fixed 5 volts. Yours is 4.99 which is fine just the same. Output should go up from 1 /1.5 volts to max 3or 4 or 4.99 (depending in how hard you accellerate) only during accelleration.from 30 to 50. Once you reach 50 and you release the pedal slightly to stay at 50, the MAP goes back to 1 to 1.5 depending on the car - and fuel mixture becomes less rich. . So in your case your ECU is thinking that you are accelerating all of the time and your fuel consumpltin must be very high. You have to replace that MAP

[@mtbshig3081]

What spray did you use to check for a air leak?

[@BrigidSamhain]

squirrels ate through MAP wiring in Buick 2009 Allure cxl. Do I need to replace all the wiring? or repair?

[@nickamarit]

How do you do this with cars with DBW? Do you have to physically depress the gas pedal?

[@davidessien5465]

Nice video! ❤ However, to check for air leak it's better to use a smoke machine to avoid hazard.

[@hacks5093]

I have a VW Golf 2.0 1995 and my car over heats quickly and I cleaned the MaF already. any chance i need a new once?

[@gondolacrescent5]

What about your coolant systems thermostat? Any chance you have air pockets in the coolant system? Have you recently done any work involving the coolant system (coolant was removed or escaped and you replaced it). what about the radiator fan? Does it work if you isolate the wiring to it by removing the wiring connector and apply power directly from the car battery or a 12-15 volt d.c. supply? Is there a problem with the wiring connector or the wiring harness? Is the radiator fans' relay broken? Test it with a multi meter or if your car has an identical relay for something that can be "sacrificed" momentarily, like the headlights (and you know the headlight relay works because your headlights turn on and off) insert it into the radiators relay position and allow the cooling system to heat up. If the fan activates before the car arrives at the accelerated rate of heating you report, re-install the relays and move onto the coolant or water temperature sensor that measures the coolant after it leaves the radiator or before it re-enters the engine. If this sensor works correctly it sends a signal to the radiator fans relay (which is confirmed as "working") at or very close to the cars intended threshold for operation at the optimum coolant temperature. If that all checks out, have a look at the radiator filler cap. Is it clogged with debris? Is the rubber gasket ok? Does the spring appear to work correctly by consistently returning to its rest position after repeated manual compressioi? Oh--do you have enough coolant in the radiator? Is the overflow tube leading from the radiator cap intact and able to transfer coolant back and forth between the radiator and the overflow tank? I'm scratching the surface of items related to the coolant system and as you've likely sensed, I'm not a mechanic but start with my suggested diagnostic chain and act accordingly. Good luck--hopefully it's something simple, inexpensive to repair--like a wiring harness that's not quite making contact with a wiring connector-just push it together until you hear a click and all should be good--assuming there's only one coolant related problem--never assume there's only one or two problems. When diagnosing anything, assumptions of correct operation of a component that was then currently unconfirmed may form the basis of an incorrect diagnosis and needless costly reaction in terms of parts and labour that will not correct the problem and possibly compound the frustration you likely feel and add confusion of thought to a reasoned process of diagnosis that leaves no room for guessing, wishful thinking, or unconfirmed results in test procedures.

[@LuisRodriguez-qm3dk]

replace the reservoir cap it could be that

[@gondolacrescent5]

yep....that too.

[@nosurrender7275]

Hacks509 overheating is not a mass air floe sensor issue...coolant level/mixture....water pump, thermostat stuck shut, coolant temp sensor, fan , and even a bad temp gouge itself are related to the operating temp...

[@nosurrender7275]

And you could have a bad head gasket...worst case scenario

[@blossmctoss]

Hi I got problem with diesel 2.0 tdi ,no error codes up or check engine light .but hesitate some times as I accelerate .people saying throttle body throttle position sensor canes in turbo clogged up lots different faults 2012 gt tdi each fault tell me about doesn't have the same symptoms and no error code for that fault is evident .obviously I will check the maf sensor like you have demonstrated. But weird thing no code .loses acceleration, just either put foot flat down on gas it picks up mainly if I gear down it works fine picks up speed as normal .also theys switch on accelerator pedal as well . Main thing confused me was no error codes come up .only time error code came up car was shuddering was glow plug light on dash. Other time code think was p0121 the code was for throttle position sensor. Never come up since .car runs perfectly again no codes but odd times does this loss of wont rev passed 2000/2500 revs .just wondering if has rough idea .possibly after car warms up to normal operating temperature. Also another thing said could be coolant temperature sensor 🤔

[@Ajab-Khan]

I have a fluctuating idle on my 2000 Camry since one year, the idle fluctuates between 650 and 480/500, which sometimes causes pressure light to flicker under load. It had the issue when I bought it and still have it. I ruled out IAC, Air Temp sensor, coolant sensor and PCV value. I'm planning to get a MAP from scrapyard and check with that. Anything I might be missing? My car doesn't have O2 sensor in the front like this car has, it has the Resistor Variable instead. I forgot to mention, the idle fluctuates ONLY at operating temperature. It becomes normal for a while, then starts again all over.

[@dukadulence1]

how do U know that yours readings from dvom is correct,is map or maf have digital or analog signal,if have digital signal U cant read good mesurment because multimeter dont have speed to mesure so fast signal in mili seconds,if I see good that map and maf have digital signal and U read some inacurate voltage and in video we can see how multimeter have late readings on map sensor for that test U need osciloskope because of speed in MS Sorry for my writings if I spell something bad I am from Europe tnx

[@MafiZed]

I'm getting 5v constant on 2 wires, thoughts? Mercedes b200 turbo

[@marcoaaguilera2620]

Very good video -Good instructor & very knowable.

[@divineentity223]

So it shouldn't have continuity in the ground and signal wire without any key?

[@Eddythe_Eagle]

Hi .I have a 2010 elantra and a launch 123i scanner. Rough idle , drives ok, but poor gas mileage . O volt reading when opening throttle. Disconnected MAF sensor, idles smooths out. Put sensor back in , now gets volt reading, idles better! Did clean the MAF made no difference. Am going to retest MAF sensor Volts with scanner in a complete drive cycle. What do you suggest now? Thanks