Check Engine Light? System Too Lean - Code P0171 or P0174 on Your Car or Truck
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- เผยแพร่เมื่อ 2 ต.ค. 2024
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Your check engine light is on, and you got the code P0171 or P0174, "system too lean." That means your vehicle's engine does not have enough fuel for the amount of air it is getting; a lean mixture. An engine running lean can have a negative impact on performance, and can cause damage! In this video, Andy walks you through the steps of diagnosing and resolving the different problems that could cause this code, from the simple: a loose intake fitting or hose; to the more complex: a faulty fuel injector or oxygen sensor.
Find your make and model in our playlists to see if we have a video on intakes, fuel injectors, or oxygen sensors for your specific vehicle:
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Thanks for your advice! That was exactly what happened to my van after belt replacement. Fixed myself!
Watch out for the A1 out they are scammers. They fucked up my car and they kept on sending a supplemental claim to my insurance every often. All when I've had a seizure attack and I was in the rehab. A1 AUTO YOU RUN SOUTH.
I have checked EVERYTHING imaginable, have found nothing bad, and still get these two codes.
And the truck runs smooth as can be.
Check engine light was on so i lifted the hood and it was still there. Imagine that!!!
Check engine came on for me 2 separate times years apart, dont remember the codes but light went off by itself a few days later. Now I'm a certified Mechinix
😂😂😂
Me too🤗😳
same here 😢
does anyone have a fix for this!?!
Good job that you checked that
I had a P0174 code on a Dodge Dakota 2003, 3.9 V6, it was running rough and occasionally would throw other codes and backfire. After watching this video I went to work with the carb cleaner and noticed a leak between injectors 3 and 6, it turned out to be loose intake screws in the area, I retorqued and problem solved! Thank you.
This is so amazing! I've been a shade tree mechanic since I was a kid. I basically just learn everything as I go. In fact, I'd even so far as estimate the 30-% +/- of the money I spend on every project is on oopsies and lesson learn. But for vacuum leaks I've always had to pay someone to smoke test it for me. Using your method I just found it in 5 minutes!
You're the only guy that starts at the beginning of the airflow and works it through that way. Everyone else starts at the 02 sensors and works back through electronically.... If the air isn't right going in at the first monitoring point, nothing is gonna come into alignment electronically. Thanks again for a clear, concise, orderly troubleshoot and repair!
I hope these tips help someone.
Sometimes if it's not the vacuum lines or the mass air flow sensor it could also be a clogged fuel filter, fuel pump, injectors or the high fuel pressure regulator. If that doesn't fix the issue a corroded or a bad coolant temperature sensor can also trigger P0171 becausen it won't read the right temperature and it will mess with air and gas mixture by sending false information to engine's computer and that will lead the car to rough idles and throw P0171. In my case I cleaned the mass air flow sensor, I inspected the evap hoses for any leaks and I still kept getting P0171. Based on all the videos I've watched on TH-cam not a single mechanic has mentioned the corroded coolant temperature sensor and that happened to be the problem on my 2005 MK4 VW Jetta 2.0L After changing the coolant temperature sensor the car worked fine and the code never came back.
Dude..thanks!!I guarantee that's my problem I never thought about em getting clogged since their pretty new.
I sorted my P0171 by replacing the fuel filter after watching one of your videos. O2, maf, ignition, vacuum and exhaust system checked out.
1A Auto videos are a huge help and very professional, thank you!
Started looking into my 2005 Rendezvous that had sat a while. First code was for the P0175 code to change the O2 sensor 1 bank 1.( I should've watched this video first.)
Changed the sensor, cleared the code, good for a couple days. Then it threw a vacuum leak code, found a kinked vac line, so changed that. Today the P0171 code and found your video.
Wish I could send a couple pics of what I found. Chipmunks built a nest in the airfilter box and also plugged the duct screen to the mass airflow sensor! Vermin!!!
Also with Fuel Injectors the O-rings could be defective ( cracked or shrunk ) allowing a lean condition as well. Sometimes you can get away with spraying PB Blaster depending on the O-ring condition which will swell an O-ring and provide a temporary fix till you replace them. I did have that happen on a 4.0 Jeep ZJ but it showed as a misfire code.
Wow!! This video just made my day. Opened the hood and realize the intake hose was loose and I tightened it back up and problem solved!! I can’t give this video enough likes
Your advice was excellent! Out of the 10 or so things that could have caused P0174, you suggested first checking every place where air could enter the system after the MAF. Sure enough the oil change guys had left a tube off the air filter box when they changed the filter. Popped it back on and what do you know! code gone. You saved me about $300 on a service call -- thanks for the common sense video.
1A auto you guys are the best all of your videos very comprehensive and easy to follow
thank you for this. recently installed a new PCV on my crosstrek and got the p0171 after relearning the idle. Checked all the connections and air hoses .. lo and behold, when I reinstalled the rubber tube that runs down to the PCV flange, the tube cracked. I definitely would still be scratching my head if you hadn't given me the confidence to really inspect the air intake system thoroughly. Thanks!
Thanks Buddy, my engine light just went on, checked it with code reading PO171 system too lean. didn't know what the issue may have been, but you just solved my worries. you're Awesome. Thanks Again
I just got the same code today, what did you do to fix? I tightened my air filter box and also had a hose like the one he shows disconnected going to see how it drives in the morning
thank you for making your videos straight forward clear and to the point, with out all the extra jargon.
MUST READ! I was going crazy trying to get that error code fixed. I have a 03 v6 4.2 and turns out the leak came from bolt bushings at passenger side intake lower portion. Ford released a service bulletin TSB 04-17-04. Hope this helps for anyone who struggled as much as I did.
Did you have to take the upper intake manifold off to put new bushings in? And do you have the plastic or aluminum manifold?
This is the most elaborate video on the subject that I have seen. So clear, detailed, comprehensive. I have a P2177 system too lean off idle bank 1. I have noticed passed 3 months that the vehicle doesn't start easily as it bid before. It now starts on third or fourth attempt. I am guessing it is more to do with fuel delivery than oxygen sensor.
+Friday Mwamba Thanks for checking us out and the feedback! If you are having troubles getting this to crank over it sounds like possibly an issue with a fuel injector(s) or the fuel pump not working as it should (low pressure). Having this diagnosed is the best way to figure out exactly what is causing this rather than replacing one part and it being another. 1aauto.com
Very helpful & detailed video. Walk through was very straight forward and easy to understand. Hopefully I will be able to fix my truck & get rid of those code. I’ll be back with an update soon!
As usual, very instructive, clear, concise. Always check easy things first, that's my motto with any repair and you nailed it on my issue. As at the beginning of the clip, it was only the MAF that got loose at the air filter box. Put it back, cleared the code. Hopefully it was only that and nothing else comes up. Thanks for your precious help!
+Martin Beaumont Thank you! We love empowering our customers and showing how to perform DIY auto repairs with our high-quality auto parts. 1aau.to/m/Shop-1AAuto-c
Super!!!. Your delivery is off the hook. Thanks man.
Thanks, got these same codes, and it was in fact a bad hose going from the valve cover to the top of the manifold on my chevy silverado 2007 4.8l Thanks!
Thank you @1AAuto , this assisted me in finding an intake leak after I had replaced the air filter causing both the P0171/0174 code as well as "Stabilatrak & Service Traction Control" errors on my 2007 Escalade.
3 turns to get my vehicle started every morning.
po171 code system too lean (bank 1). DTC Severity 2of 3. Help?
Po174 system to lean (bank 2)
Po420 catalyst system efficiently below threshold
Fairly new fuel pump 2yrs old
Changed air filter and MAF
Occasional jerking, and knocking while driving,low acceleration, some stalling when jerking . 08 Ford expedition 5.4 V8
You have given me the confidence to repair myself . I would like a better idea or suggestion to my problem? Thank you so much
Erin, did you figure it out? I am literally dealing with the same issue. The crackup here is that the error code is super vague. Even his video lists so many things it could be rather than an isolated issue like the code would suggest. For instance Why would it say Bank1 if it could be the MAF or why would it identify Bank1 if it's a gasket leak like he was testing for in his video. Bank1 is pretty specific in engine terms, right?
P0171 with intermittent Check Engine light on my 2000 Pontiac Montana with the GM 3400 SFI here. I found a rubber vacuum cap on the upper intake manifold that was turning into dust and mush. Sure enough, there was a pinhole of light visible through the cap. Just replaced it. Unfortunately, I also have a P0452 that’s likely from the replacement fuel the shop put in last year. It was making a high-pitched whine from the start and the shop refuses to warranty it just because it’s technically still working.
Great video, informative and easy to understand. Subscribed.
Thank you, that was perfect, becouse my car is doing that, so now i know wat to do thank you, big help
The dealership wants 300.00 to fix this. Is it something I can do on my own? You make it look easy.
Thank you for the run through possible issues regarding those codes. Very detailed and understandable. Great job, keep up the good work
Thanks for the information. I really dug your character, Cyrus The Virus in Con Air. Say hi to Nick Cage for me.
Thank You! A hose leading to the snorkel was disconnected! I had Code P0171 and P0174
My friends Lexus has a torn open hose between the air filter and intake.
+Robert DIY Thanks for the feedback!
I was getting this code and random stalls on my 03 silhouette. New mass airflow sensor for 30 bucks fixed it.
+RamenNoodles4Me Thanks for checking us out! 1AAuto.com
Hey how did you figure out it was that?
I have an 01 ranger and has that code thank you
It is an excellent video in relationship to these particular codes much more thorough than any I've seen and especially appreciate you referencing the front 02 sensors as a potential problem.
What about having excessive fuel additive in the fuel? Will that create the code? Awesome video very informative.
I'm thinking that could be my issue too. I added 2 different types of additives
Incredibly detailed and helpful video.
+Tree Garden Life Thanks for the feedback!
I fix my truck Nissan Pathfinder 2009 with code p0174 p0171 i changed the gas cap and fixed
I know this is random but that "old school" vortec engine makes me smile. I can never understand why GM did away with those engines.
They are dependable engines . I have 375k on my 5.7
Best mechanic 💪🏻
I haven't checked any of this on the car yet but I have to say that was very informative and gives me a really clear process to follow. Thank you!
My 2006 2500 HD had a P0171 Code, I took the cover off the top of the engine, started the truck and immediately heard a leak from the drivers side hose connected from the engine plenum to the valve cover, thanks to this video, I found it pretty quick and fix the leaking hose.
I should have gone to school for this very interesting
What if I have the P0174 code and a strong odor/smell of gasoline as well when the car is running? Would this imply there is gas leaking out somewhere? If so how best to check /find location of a gas leak? Thanks.
Yes that would be a gas leak, check ur gas hose,,
guys i been battling po171 code for 3 months now im dying and suffering i changed MAF sensor, did smoke test no leaks, change spark plugs..midas dont know whats wrong with it lols..any one can help ? lols thanks!
Very helpful, I had a couple loose vacuum hoses and the airbox not properly sealed.
excellent! very complete - THANKS
Do these codes cause your vehicle not to star? Because they are doing it for me
My 2013 Sierra 1500 just had a P0174 code, I can check all what you just covered over, I hope it doesn't end up being a lazy fuel pump. But I don't think it could because I can hear the pump engage when I turn the key on and the engines cranks up always on the first turn of the key, a fuel pressure check should indicate if it is though.
Got that number my Honda cr-v 2000 5 speed don now what need to fit don't see any air coming no where thin can be thank you video
Trying to get everyone’s insight, where should I look if I’m getting both codes? Bank 1 and 2 lean!
Thanks very helpful and nice touch at the end 😂! Any videos on P0300 with others like P0302, 4, 6?
2nd vehicle was a 3.6 traverse or equivalent for sure. I've seen those more than I'd like and it's only been mine. 😂
Good starting point. The P0171 and P0174 are basically the same code. The difference in the number is another troubleshooting hint. 0171 USUALLY Bank 1. 0174 Bank 2. This is for V type engines. Consult
Your factory service manual for the layout.
Rear Whee Drive vehicles the banks are side of the vehicle and although should be standardized not necessarily so.
The general layout for my RWD V6 for example Bank 1 is on the passenger side of the engine compartment looking forward from the drivers seat.
ALwAYS check the layout, mine is 1-2-3 on the passenger side and 4-5-6 on the drivers side. Some might be 1-3-5 and 2-4-6.......
DO NOT confuse cylinder layout with firing order.
I just got a P0174 and cleared for now. When the weather gets better I will check in more detail but not panicking yet!
Thank You, greatly appreciated your video
Thank u for that, very easy to, understand.
QUESTION!!!
What if your engine has two banks but the code is only for one of those two banks?
So p0174, would that probably be a faulty injector?
Checked everything. No tears, nothing loose, no performance issue. Just a check engine light that came on while driving and p0171 code only. What now?
Exellent video
+konstantinus Stoyanov Thanks for checking us out! 1AAuto.com
Hi, i checked mine for vacuum leak all the hoses and didnt have any leak, but still threw a p0171 after driving 15miles.
Thank you
Mines turned out to be my fuel pump. Wasnt getting enough fuel for new but i found vacuum leaks along the way the check engine light didn't disappear until i found out about the fuel pump pressure bring low
Was it a new fuel pump joss
Boss or the old one?
nicely explained. thanks
What about if I only have p0174 code
Thanks for narrowing it down to about 10 different things
Very informative video thank you very much
Thank you for this video. Po174 came up on my 99 gmc the other day. I had just had a new rotor and distributor cap installed and your instruction lead me to a hose that the mechanic forgot to reconnect. I did and it’s running like a sewing machine.
Apparently you missed an obvious problem that is very common, broken exhaust bolts will cause a po174, oxygen being drawn into exhaust stream, step it up, get it all covered.
Help! I have a PO 171 code mystery no one can solve. I have a 2000 Buick Park Avenue Ultra. 121,000 miles. Well cared for all its life. However, the service engine light came on a few months ago and it’s showing left bank 1 too lean.
I have taken my car to two Buick dealers and five independent mechanics. No one at all can find the problem, but something is clearly wrong.
Here’s what’s been checked, replaced, repaired so far:
-Both O2 sensors are perfectly fine; the post cat sensor is new. The pre cat sensor was tested and is working (apparently) fine.
-MAF has been cleaned. Apparently works fine.
-Fuel filter changed; fuel system cleaned.
-Spark plugs and wires changed.
-Catalytic converter replaced and the previous one was in fact bad.
-No vacuum leaks.
-No injector problems.
-No fuel pump problems.
-No fuel pressure problems.
-All the numbers on the computer are registering normal.
-Car runs like brand new now, but the light won’t go out and no one can find anything wrong.
-The valve cover and supercharger gaskets have very slight leaks, but I’m told not enough to suck in that much unmetered air.
A fuel sample revealed E85 gasoline in my tank, but I’ve filled at tons of different stations in the last few months, always and only 93 Unleaded, so there can’t actually be E85 in my tank.
If the light is still on after $2000 worth of work and diagnostics? Then something must be wrong. Is anyone out there (like anyone at all) who can help solve this mystery? I love the car and it’s in beautiful condition, but I don’t know what to do at this point except dump it and get a new car.
Help!
These were very good tips. I was ready to go by two oxygen sensors, but after watching this video and I checked all the lines and hoses I found one hose disconnected and I reconnected it solved my problem. Thank you very much.
Im convinced my purge valve is causing this code because i also got the P0456 code along with this code indicating a gas emission vacuum leak , can that be it?
You did it 👏 🙌!!!!
So if I hear you correctly there is virutally no difference between the P0171 or the P0174?
For instance my code reads "System Too Lean Bank 1"
I have same vortec engine , after replacement of
new filters (both),
new o2 all (4 ),maf sensör , pvc valve(valve cover) eng.light is not coming back.
But fuel ratio still to high , and consuming more fuel.
Fuel pump pressure ok.
All enjektors active.
No air leak.
Last thing I'm gonna do, clean or replace all enjektors. 💰.
I need to find one video on changing out a evap canister on a 2012 Dodge ram 2500
Great Tips Thanks 😉👍🏽⚙️🔧
Great video. Not covered, can a gas cap, vent problem cause a lean code as well? Since low fuel delivery would result in lean as well?
How bad is it to keep driving my 05 chevy cobalt for now until i have someone look at it
i’m getting codes p0171 & p0174 when i’m driving at lower speeds you can hear loud air noise and the rpms go up and past gears
Could a restriction in the exhaust cause lean code
Thanks again for the tips this Chanel saved me a lot of money god bless everyone
What if it's both at the same time? Also installed new MAF sensor, fuel filter and no vacuum leaks to be found.
You are in part changing mode already.
I installed an aftermarket cold air intake in my 2003 Silverado I hooked my scanner to obd2 just to watch what’s happening while I test drove. So I drove down the street to jack in the box while at drive thru scanner red light went on and o2 senors readings stop right away I scanned for codes and got P0151 & P0157 as Pending Codes (Mind u No Check Engine light on dashboard) I Didn’t notice any negative changes in the engine or it’s drive ability, Why Would These Codes Have Popped Up?
I did the same it maybe be a bad cat
Oxygen sensor
Could be a misfire in one bank. Not a good idea to replace parts based on a code without finding the actual problem. An O2 sensor code can be triggered for many reasons. Why replace the MAF unless you know it's bad. Could be a bad injector in Bank 1, a fouled plug, or oil in your plug well due to bad value cover gaskets. These will all cause a misfire in one bank and that would cause a lean condition. I'm not directing this at the video creator. It's a great video. Very informative. This is directed at the comments of people replacing parts for no reason.
My 07 TL has a valve cover leak. Can that trigger this code?? My CEL came on today but that's for a different issue. When I plugged in the OBD2 reader I saw this code but can confirm this was not what triggered the light
Very nice video may I ask is it possible for the mass air flow sensor to be dirty that could pause it?
Well you were right
i has a question how bad is it to run with this condition? just wondering as the part that needs replacement is the throttle body gasket (in my case). Seems to be on national gelatical back order and can not get till like next week. So my resolve it 1 of 2 ways wit the few days-week or make one using form a gasket sealant. so question is should i wait for the proper part in doing so driving with this condition? or is it an issue that should be fixed prior to going any distance with the vehicle? Btw replacing a thermostat on a Rodeo or Passport is not an ez job designer's are insane IMO.
Hey, that's my engine! The GMC 5.3L. I need to replace my purge valve this weekend to fix a P0440. And while I'm under the hood, I'll clean my MAF sensor and check all my connections.
im getting those codes but no issues with the engine, my transmission kicks when changing gears 1 to 2, plus my traction and stability lights turn on and off.
Great trick. Thank you very much.
+ricky sixstring Thanks for watching!
the carb cleaner trick found my leak !! thanks for the tip !!!!! glad I watched your video !
Was curious what about the evac lines going back to the charcoal canister and what about the charcoal canister being bad was curious
Doing this how ALL car issues shoud be dealt with....you start with the "what is most probable" and from "simplest explanation" to the more complex repairs.
yep was exactly my issue. 0:51. i must have jostled this while trying to get to the headlight. :facepalm: thank you! Thank you OBD reader and thank you 1A Auto Repair. fix was all of 2 minutes
I have a 2006 Chevrolet trailblazer and check engine light was on but went off but code read p0171! Does this mean it's the fuel pump?
Another very common reason for this code is if you use the oil on a reusable air filter it can plug up your Mass Airflow Sensor. If that happens all you need to do is clean the filter, don’t use the oil anymore and clean the sensor.
+Travis Schallot Thanks for the feedback!
YES! those oiled air filters are ABUSED by low information owners. BEST solution is-- use TOP QUALITY(pony up) dry air filters, change it once or twice, depending on dirty Nevada/Arizona living areas. CLEAN air means hardly any trouble for MAF.
i have a p0171 i couldn’t figure it out so i took it to the shop they couldnt figure it out either they didna smoke test and no leaks ran diagnostics and nothing and the light turned off by itself during the testing. later that day when i was driving the light came back on same code
I HAVE 05 EXPLORER LIMITED AND WHON GO MORE THEN 20 MILES AND SHOWS ONLY PO174 what can be
Got the same code. And the light goes away after I fill the tank up full in the car. Does that mean fuel leaking or not enough fuel getting into the engine.
Would the cold weather cause that?
I have that code and the truck has a hard start
Can low oil cause these faults ?