Diagnosing a Faulty Mass Air Flow Sensor: P0171 P0174 Lean Codes

MAF Cleaner I use that is safe-
amzn.to/1W0p8ot
I only use Ford Calibrated MAF Sensors-(check fitment guide)
amzn.to/1tsbZcs
Here I show you how to clean the MAF properly-
• How To Clean A Mass Ai...
In this video we go over just how a skewed MAF looks.
My Company BSG Automotive offers Auto Repair services in the greater Chicagoland area.
Website:
www.bsgautomotive.com
Facebook:
/ bsgautomotive
Catch up with us on-
Facebook: / fordtechmakuloco
Twitter: / fordtechmak
Instagram: / fordtechmakuloco
My company KZbin Channel- BSG Automotive providing repair advice on makes and models other than Ford: / bsgautomotive1

[@SouthMainAuto]

Classic dirty MAF, rich at idle, lean at WOT. Good demo Brian and explanation. The best part about this is, is it translates across so many different makes and models too and not just Ford. Glad to hear ya got a lot going! Take Care, --Eric O.

[@spelunkerd]

Brilliant demonstration, Brian. *Rich at Rest, Lean under Load* is a catchy mantra to help remember. I stumbled, trying to understand what happens at idle. For years I've been side tracked thinking it was because the PCM had a 'memory' of prior drive cycles, but as you elegantly show the answer is more simple than that. A dirty MAF actually overestimates air flow when at the low end of the scale, in addition to underestimating air flow at the high end. Why would a dirty resistor cool more quickly during low air flow than a clean one? It's more simple than that! I'll guess, the dirt and oil actually impregnates the resistor to increase baseline resistance values.

[@radleybradford1356]

@@spelunkerd I've often thought the same, it must be impregnation.

[@dannyl2598]

Thanks again. You have given me enough information to hopefully make a good diagnosis on the problem I'm having. I greatly appreciate your help. You are my number one trusted tech on Ford's.

[@lakenseagt]

Thanks for the great info. My 2002 Sable was showing codes for lean on both banks. I had downloaded a Ford tech sheet for troubleshooting, but hadn't started yet. I happened to watch this video and decided to try cleaning the MAF. After cleaning the MAF, clearing codes, & resetting computer the codes were gone and still gone after 1 week and many trips. Much cheaper and easier fix than I anticipated. I've been following for a while and greatly appreciate your detailed videos and great explanations! Keep up the good work!!

[@ReclusiveMountainMan]

Brian,You're a good teacher. If you ever decide to retire in the far off future, maybe a career as a community college instructor would be a no-brainer.

[@1keykneedeep]

Great information Brian. Its almost like you were using my vehicle for thus video. Same engine with same problems. And the same fix thanks to you. My truck didnt love the K&N filter and the maf was filthy.

[@hawaiianf1504]

Brian You're Just Amazing. I watched this several times and each time it got clearer and I understood more and more. I think my son would have gotten it right off the starting line. It wasn't you or your video, both of which was awesome. It was only my cranial ass mask getting stuck again. After I reached 50, I learned how to use that mask to store words of wisdom as well as tips and tricks and I think I must of ran outta room and didn't know it. I think as we get older our brain cells get slower. Seriously slower. I am sure glad we have folks who are as sharp as you are doing these types of jobs. Us old folks just ain't got that many BB's left to handle this kind of work.

[@SaadElectric700]

Great work my friend a beautiful piece of information Thank you

[@Hugh_Manitee]

I was getting a P0174 code (lean on bank 2) on a 07 F150 4.2l. O'Reilly's diagnostic. I changed fuel filter and erased the code(removed neg. battery cable). Check engine light went off. A week later it came back on. I got a fresh tank of gas and a bottle of Lucas Fuel injector cleaner. After about 2 hours of driving it, the Check Engine Light went off again. So far, it's still off for 3 days. We'll see. I start with the cheapest fixes first. 😀👍

[@markchimmy]

Did your check engine light ever came back after you filled up and put Lucas fuel injection cleaner in? Thank you!

[@airborne63]

Thanks so much for the info. My Crown Vic was running lean, and missing at idle. After watching this, I checked the MAF with KOEO...and found that the voltage was 0.23, and was reading 2.5 grams of airflow.... Replaced it, was 0.01v...to zero....no airflow. Short and Long-term fuel returned to normal, as well as the idle. Thanks again.

[@markferraro5250]

great video Brian thanks so much one thing to add is to look at MAF pid in grams per second along with voltage on scan graph take care

[@joeyedwards4012]

Dude your the man, love your videos and explanations. 02 f150 4.2 been down for a week and driving me nuts. Wish you were my neighbor!!!!!!

[@michaelcook9920]

Great video explained everything really well really enjoy watching your videos keep up the good work

[@glasseyi]

Love your videos Brian. Keep up the great work.

[@miamidave3081]

Well done this was a big help good work my Ford Expedition is doing the same thing

[@ClydeBickford]

Amazing video, exactly the problem I've got with my Subaru Forester 2.0XT, poor performance / hesitation on acceleration, and guzzling tons of fuel. With the engine OFF, MAF reads a steady 0.24V. Then, after engine ON, it jumps up to ~0.95V initially, then tapers down to ~0.8V. At ~2000rpm's it gets up to ~1.6V. Several weeks prior, I had already purchased the CRC MAF sensor cleaner, and cleaned the MAF and MAP sensors to see if that made a difference, but it was long before I started studying the data and thus I didn't know the readings were abnormal. When I did start looking into the data, I first found that both O2 sensor readings had been all over the place, and I proceeded to replace the rear sensor, only to find the same behavior.

[@rogermartin2176]

When I turned my key to the on position /engine off, I read on MAF sensor .23 and also when I unplugged it, It still reads .23. So to see if the car knows that it is installed I drove with if off. It threw a code that it was so I thought that the wires were electrically fine. I then brought a new MAF sensor and plug it in and it too is reading the same thing .23 along with high Lt fuel trims... Thanks for all your videos they have pointed me in the right direction.

[@boppzoli]

Hi!I have a 2004, Ford Focus Mk1, with 1.8 tdci 85 Kw engine (european version, MK1 facelift).Based on your video I have checked the MAF on my car and it reads 0.059V. Is this good or I must change the MAF? I noticed a bit of power-drop in high rev range (3500-4400 RPM) in the last year, but the fuel consumption and the overall performance are still OK. The car has 312.000 KMs now without any intervention to engine, and no need to top up between the oil changes ...Thank you in advance!

[@sandyande]

cheer's Brian had a diesel ford cmax 1.8 here in the UK the only way I could prove it was air mass meter was to disconnect it and it then went like a rocket. it was not voltage but frequency between 1khz to 7 kHz, sandy

[@psfphotography]

I have a 2001 Expedition with 167K miles with the 5.4 that I believe gave the same codes. Would it make sense to clean the MAFS or replace it given the mileage of the truck? Thanks, Paul.

[@jesusblanco746]

muy bueno el vídeo saludos!!!

[@boppzoli]

Sorry to double my post, but I really need your opinion ... Thank you in advance!Hi!I have a 2004, Ford Focus Mk1, with 1.8 tdci 85 Kw engine (european version, MK1 facelift).Based on your video I have checked the MAF on my car and it reads 0.059V. Is this good or I must change the MAF? I noticed a bit of power-drop in high rev range (3500-4400 RPM) in the last year, but the fuel consumption and the overall performance are still OK. The car has 312.000 KMs now without any intervention to engine, and no need to top up between the oil changes ...Thank you in advance!

[@luisbaez88]

most of the time i get ford with p0171 and p0174 is do it tps out range a vacuum leak from idle valve breather or intake gasket itself and dirty mas sensor. good video.

[@daleselko8680]

Ķ

[@Bigbuddyjoe]

Great video ! I have a 2000 ford ranger 2.5l with a lean code. The mass air flow sensor is reading 0.50 g/s with engine off and 2.21 g/s with engine on at idle. Is those normal readings ?

[@jaywillsey6797]

MAF for 2004 Expedition is no longer manufactured by Ford. I bought aftermarket. Question, to verify you said ignition on engine not running, MAF airflow should be 0.0? My original one shows 0.4 and the aftermarket Walker showed 0.8 to 1.0. Subsequently my fuel trims equal 30-40. Do I have two faulty MAF sensors? Or something else? No vacuum leaks found. Your videos have taught me so much, thank you for all your help keeping my Expedition going with 224K miles.

[@javaidmalik1]

Thanks for your best information sharing with us on of best video I ever seen this is good to fix car 90% globly

[@OnTheGoLoft]

ive been following u for a while as well . Love ur vids....

[@slideman.]

Amazing! Thanks FordTechMakuloco!! For the past 6 months I'm struggling with high gas consumption on my 10 year old Fusion V6. The dealers did not find anything and wanted to throw a lot of parts at it. I don't have a scan tool but I can try this. Thanks.

[@CARRJ142]

Another great video.

[@tamyboy1]

Great Video

[@pablomarquez4431]

Great info. Yea I think thats the problem I got. It only throwing a lean code in bank 1 P0171 on my v6. No maf codes. But my lg term trim in bank 1 is 14.1% and 13.3 % in bank 2. I revved it up to 3k for 1 min and my lg terms didn't change. But my idle reading at idle is .40 lbs/min .. I think it's under performing.

[@rexluongo6470]

I have a 2006 F250 5.4L 3v, my MAF voltage is 0.00 KOEO. When I start it and let the idle settle down into normal idle I have 0.78-0.85 volts. My Baro at 430' above sea level is 148 at idle. I have normal fuel trim at idle but the second I give it any gas the fuel trim shoots up to 25-50 overall fuel trim. It has the same instant response you are talking about in this video. I checked fuel pressure it's good at 40psi and 75 psi KOEO. O2 sensors also read lean on wot test. Do you think my MAF is functioning properly? I also have a rough idle and sluggish acceleration on take off but seems to smooth out and run better at higher rpm. Again, fuel trim is good at idle only. Already checked for typical vacuum leaks, there were none. The MAF is new, purchased from Oreilly auto parts, I admit, I did buy the $69 MAF. Ford wants $230 for theirs. That's my price anyways, I imagine you get better pricing then I do as a mechanic. Plus probably helps to not be PE1 🙂

[@mesacox8875]

I recently took my 4.6 2v 98 f 150 to the shop because it has a rpm bounce at wot and none of my local shops can figure it out, I’m stumped. Have replaced lots of things and it has no codes displayed. Was wondering if you had any ideas

[@mummaistvan7320]

2009 Ford Escape 3.0l. #1 code P0174 bank 2 lean #4 code P0304 . Spark plugs, ignition coils, fuel injectors all new! Cleaned EGR valve. Have cleaned MAF twice past 4 months. LTFT +7-10 %, LTFT2 stuck at 29 %. Doesn't change? Both STFT perfect. Had misfire code first. After new parts etc P0174 bank 2 lean. Air filter new! MAF obd 2 MAF 2-3.34 g/s idle, 2000 rmp jumps 2.9-8.8 g/s! I'm assuming the MAF SENSOR today! Idles rough. Starts great, no loss power?

[@ztensa]

Hey, love your videos but I have a reader that doesn't read the maf voltage, only the air flow rate. So at key on, engine off its reading at 0.5g/s. Is this okay?

[@masterofnone7846]

Very informative video!!👍👍

[@mullinsjm1]

My 98 5.4l has these same codes. Is there a way to tell maf voltage on the cheap wifi/bt scanners?

[@bradvincet1848]

Why do you suspect bluetooth is the problem? I'm having the same issue.

[@vn1500g3]

Speaking of driveability issues, what would I need to look for in a vehicle that is surging? I have two vehicles that exhibit the same problems. Both are Ford. One is 1996 Ford Contour, manual trans. with 117K on it and a 2002 ford Explorer with 190K (you've helped me with this one before). Fuel pressures are good, new clean FORD air filters, fresh plugs, and quality fuel. Seems to be more pronounced when the vehicles are coming up to temp. Never completely goes away, but gets less severe. I'm thinking wonky O2 sensors?

[@vn1500g3]

Thank you! It never occurred to me to suspect the DPFE. I will definitely test them to see if it has an effect on both my Contour and my Explorer.

[@ozzstars_cars]

Great video man, thanks for posting

[@grasscutter1963]

Alright, I’m confused... I have a 2005 F150 4.6L six pin maf sensor . I have tried cleaning it with the cleaner spray, no change. Tried the method with truck running unplug the mass air flow sensor and it kept running and what a video told me is it’s bad if the truck stays running. So then I tried the other method as where you figured out your power, ground and signal wires. When I test the signal wires with meter and press the gas peddle slowly and release slowly it shows me that it’s good.... which method is correct??? Thanks

[@exile9237]

Would a faulty MAF give you a code? I have a 05 mustang gt thats running like crap and is not throwing any codes. I recently replaced the throttle body and didnt help one bit. My idle is actually sometimes lower than usual and it runs very sluggish on take off. Every so often it randomly runs ok out of knowhere. I have noticed that when the car is running bad the shifting feels clunky and rough but if it runs good it shift nicely. Taking off in firstgear is a drag cus it seems like the rpms just want to drop any thoughts?? Most shops out here keep saying i have to go to the dealer because theres no codes and they cant diagnose the issue!! Any advice would be appreciated

[@americanpatriot5836]

Great video

[@fleettech3570]

I have a 2014 mazda bt50 turbo which is diesel. I have realised it uses a lot more diesel than normal and I also realise when I stArt it up from cold you smell a strong diesel smell from the exhaust

[@algreenejr.8330]

Hi, I recently put in a high performance Mass air flow sensor in my five hundred, it ran well and made noticable power the next day I unplugged the plug to the sensor and plugged it back in case it seemed lose, when I did that I broke a wire and didn't notice so it wouldn't start I found the break and reconnected it, it started but didn't run well and I started getting the wench light so it kept going in limp mode, why would the new sensor work well for awhile and then not run well at all? I have two holes in my bumper each going to a induction air filter and meeting at a y and heading up to the intake. I was getting lean problems after I added this, but the one thing I noticed when I was getting codes and limp mode from the map sensor there were no lean codes on the scan tool, I plan to put bigger injectors to balance the lean problem but I wish I could use the new Mass sensor without codes, lots of throttle response and power with it, I would like to hear what you think, i learn alot from your videos for my Ford, thankyou!!!.

[@kc6434]

Have 2002 F150 with 4.6. MAF reads .01v on KOEOFF. I have P0172 & P0175 rich codes. I had local garage check. say all sensors in spec. fuel pressure 32 running. The garage is telling me to check compression , that timing chain could be worn, does this sound correct?

[@tylerchapman5555]

Sorry to bother you but would you know the average trims, load, afr, lambda for a 2011 mustang 3.7 ? Also it's the blue, purple, yellow, yellow 4 pin maf sensor and I'm certain it's wired up correctly but it won't read

[@sambonno7399]

99 ford 4.6 my reading key on engine off 0.01 it's also the same when engine is idle? Im confused any advice. Thanks

[@luismorales2450]

That transmission comment funny you mentioned it. Thanks man

[@donaldpage607]

How long can I expect a MAF sensor to perform correctly

[@brentpaisley2983]

Would this reading be the same for an aftermarket sct mass air flow sensor on my mustang

[@Aloha96789]

My scan tool reports in grams of air per second. When I accelerate normally If the maf is under reporting will I get a p0171 and a p0174?

[@manuelsalgado8510]

I was getting codes for lean condition - then I cleaned the mas sensor and then the code came back at running rich, any thoughts?

[@ronell46]

I have a 2004 ford e250 van with the 5.4 liter engine I have no engine codes but im having a horn sounding noise coming from the mass air flow sensor area and i just had my transmission rebuilt and it was making this noise before the rebuild it will only make the sound when its in idle when im driving the noise goes away and i cleaned sensor with cleaner and its still making that noise.

[@MrJon10002]

im reading 1.62V with the engine off ! Ford focus st225/XR5 :o think i might need to look at this !

[@paulfiebke3909]

Is Orollys a good place get parts? And where do you get yours? Loved this video. Keep up the good work

[@FordTechMakuloco]

In general no, but I do go there often enough because they sell motorcraft parts too.

[@pappagiorgio1675]

Can you have a MAF driveability issues and NOT have a CEL? 2011 ford fusion se 2.5l

[@Manolethal2]

My 2003 expo acts like is going to turn off but never do!!! Could it be the mass flow sensor or the aic... I dont get no codes??? Pls help me out

[@dracula4733]

Wat is da normal mass air flow sensor reading at idle on a 05 f150xl. 4.6l.rwd & also cold starts up around 1500-2000 rpms on cold starts only y..????

[@pinpeobi]

Having an issue with ny 2014 F150 3.5l which seems like mass air flow issue. Around town seems fine on freeway @ 2k to 2500k rpm begins to sputter. Outside of this My truck is throwing codeP054A Cold Start "B" camshaft position timing over Bank 1 trying to figure out if it's the mans air flow sensor (which I cleaned one was gunky) ooor those camshaft position sensors can't afford to purchase them all and have no diagnostic tools any ideas?

[@charliemahoney2912]

Thank you

[@filthymcnasty75]

Hey bud, i'm a new subscriber to your channel ,great info/vids ! I have a 05 5.4 triton , that stalls well driving /all lights on dash come ,no throttle response , but will start up after a bit And will run fine , this happens once every few weeks , any advice would help ,thanks !

[@filthymcnasty75]

F-150

[@cfahelp3668]

Not going to say it's the for your problem fix but I had a dirty throttle body which caused a similar issue as yours. Cleaned it with the CRC throttle body cleaner and now idles at the proper RPM and hasn't stalled since.

[@MrSamolet76]

I got same problem on my 4.6 3 valve 2010

[@jeremygrossg.jhighgyy447]

Fuel module..mine was above spare tire..corroded

[@doitdoits4109]

First I would like to thank you so much from what I have learned from watching your videos. I have a 2003 F150 5.4 throwing P0171 and P0174 only in extreme cold conditions. I purchased an OBD2 scanner and do not see a way of reading V on the MAF but it does show g/s. My question is reading is .16 g/s key on engine off. Can anything be concluded from this reading or should it read 0?

[@edb3654]

My maf sensor on the P.I.D on idle and was stuck at .66 to .67v at hot idle is that a sign of a bad maf sensor and I do have P0171 code?

[@catfish318]

My truck readying the same codes and i have changed maf sensor oxygen senssensor still got the same problems

[@aaronq.6033]

Could a maf fail and over report air flow causing rich on both banks?

[@Penksimo]

What scanner are u using or software? would u be so kind to tell me please please!!

[@FordTechMakuloco]

Ford IDS

[@Penksimo]

tnks

[@Shapechanger101]

I have a 2003 Escape, fwd 5 speed with the zetec. If i throw it into nuetral coming to a stop the rpms will spike to about 4k and then slowly come down. the rpms will also spike about 500 when shifting. it has thrown a p0507 code. any suggestions.

[@Shapechanger101]

+2012fofusionsel I have cleaned the IAC with no results. The throttle body itself seems ok, the spring is strong and there appears to be no binding or weird spots. But with the throttle cable hooked up it seems to alow down a lot more, and it looks like it doesnt want to fully seat. I replaced the vacuum hose that has a heatshield on it that runs around the back of the engine and it did not help either.

[@Shapechanger101]

+2012fofusionsel I sadly domt have a scan tool to use. Can a bad IAC cause it to feel like the pedal is being pressed down?

[@E.J.61]

98 ford explorer sport 4.0 sohc and unplug maf and it keeps running. Is that normal?

[@bruh7376]

I have a p0102 on my 2006 f150 5.4. Please help out

[@TheEightdigits]

My MAF was reading .03V KOEO so I got a new Delphi from Rock Auto and it is reading .05V KOEO. What the heck. Is there something else going on here. Clearing codes and see how it does.

[@emmanuelestrada5914]

What scan tool are you using?

[@FordTechMakuloco]

Ford IDS

[@michaelvickers3275]

My 03 F-350 6.0l mass airflow sensor home owns out fine I have no power coming through the wires with the truck running I checked it owned it there's no power coming through with the key on anything truck running nothing no power coming from the positive side of the mass air flow sensor wire what could it be

[@mechanicallycreative9788]

What's this fuel pressure trick you speak of?

[@adammammana367]

Should I disconnect the battery while cleaning the MAF sensor?

[@yqwgjsg]

You should unplug the sensor and not plug it back in until the solvent cleaner is completely dry

[@adammammana367]

+Hammer0f Thor for sure. My 05 Mercury LSE runs very well but after cleaning the MAS I'll just be driving along and I'll think to myself, 'this car runs EFFING good'! And it does...85k miles and its perfect. I recently purchase a 02 LX Sport (last design cuz it's black with 33k miles) and the Mercury out performs it by far with the same specs. 4.6 dual exhaust 3.27 ratio. The ford just seems like a big heavy car but the Mercury seems lighter more nimble. The next panther platform would've been amazing.

[@adammammana367]

+Hammer0f Thor what I was getting at is the Merc runs better

[@ronhorvath4939]

Hi Brian, been watching your vids off and on for awhile. Anyways i was wondering is forscan and ids the same thing? Just ordered a obd2 scanner for my laptop to try out forscan for my vehicles

[@FordTechMakuloco]

No the IDS software is a top of the line professional software. The forscan software is a basic DIY scan tool.

[@ronhorvath4939]

@@FordTechMakuloco okay thank you. My usb scan tool just came in i think it will work for what i am needing. Thank you again for all the amazing info that you put out.

[@mikerossmiles2011]

My 2013 F-150 with 3.5 Ecoboost with 66000 miles has an issue showing P2096: POST CATALYST FUEL TRIM SYSTEM TOO LEAN BANK 1. Repair shop 1 replaced the Bank 1 O2 sensor and the engine light was not lit for the next few hundred miles of driving. Then the P2096: POST CATALYST FUEL TRIM SYSTEM TOO LEAN BANK 1 returned. The repair shop 1 spent 3 or more hours diagnosing issue and stated both Bank 1 and 2 have the same lean condition and suggested taking it to Ford dealer. I recently took the truck to the Ford repair center and they replaced the O2 sensor for bank 1 and the engine light with the P2096 code returned after driving 70 miles. My $20.00 code reader will clear the error code, but it comes back after 10 to 20 miles of driving. The truck runs fine and smooth, but has lost about 2 miles per gallon on gas mileage since this error started at the 63000 miles timeframe. I've cleaned the Mass Airflow sensors and that did not help to resolve error code. All suggestions are greatly appreciated and wish I had a skilled diagnostics specialist like you and Eric O is my area. Thanks, Mike M

[@everygoodtree]

Is it common to see conflicting lean and rich codes? I'm getting P0171 and P0174 with P0172 and P0175. I cleared the codes and the lean codes were the first ones that come up. I don't know if I'm seeing some kind of overcompensation or what. I can't really find anything on conflicting codes. I am also have a rolling idle, poor power and performance, especially on acceleration. Driving a 2006 E350 5.4L with 140,000 miles. BTW this started after a fill up, so I was also thinking bad fuel, but I've been through a couple fill ups since. I inspected the MAF sensor and doesn't seem to be dirty, but I'm going to clean it anyway and install a new air filter since I didn't at my 140,000 mile oil change before a this long drive during a vacation. Any wisdom would be greatly appreciated.

[@everygoodtree]

Also making sure...there are 2 cracks in the air filter housing. I would think that the filter would seal these off and they are also pre MAF. Would that be a problem?

[@everygoodtree]

Cleaned the MAF scensor and these codes dissapeared. But 3 weeks later I'm having P0306 and P0356, can't help but think they're related. Going to check out my coil on cylinder 6, spark plug and fuel injector, plus wiring. Any help would be great!

[@codyramos3200]

i have no long term ft readings . an my short terms are way off from bank 1 an bank 2 bank 2 is like 30 an bank 1 is 5 to a negative number

[@whatifyourwrong9153]

I can’t find Motorcraft MAF sensor for 99 5.4 to buy 🤦‍♂️

[@mrbakerskatz]

Thanks for the good info . I think I'll change my K&N filter for the MotorCraft filter .I wish I'da known before I purchased it . I've run K&N for years in all my GM vehicles with no problems but they aren't finicky lil bitches like fords are .

[@mrbakerskatz]

***** Thanks Jonathan , The problems will come when you reoil the K&N, Too little oil will hurt filtration and too much will damage the MAFS ,or so I've been told by above .

[@Anthonythesider]

I don’t have a code

[@MC-hs4mf]

??

[@charlesberlanga4452]

TOOOOO technical.

[@massagegirl30]

Mine is reading 0.008v at key on engine off. Does that mean the MAF sensor needs replaced being that low or maybe just cleaned?