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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!

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.

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 KZfaq 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.

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.

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.

I sorted my P0171 by replacing the fuel filter after watching one of your videos. O2, maf, ignition, vacuum and exhaust system checked out.

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.

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!

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.

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!

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!

I have checked EVERYTHING imaginable, have found nothing bad, and still get these two codes. And the truck runs smooth as can be.

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.

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.

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!!!

Thanks for narrowing it down to about 10 different things

Thank you for the run through possible issues regarding those codes. Very detailed and understandable. Great job, keep up the good work

Check engine light was on so i lifted the hood and it was still there. Imagine that!!!

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.

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!

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 for making your videos straight forward clear and to the point, with out all the extra jargon.

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

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.

Great video!!! Can’t wait to troubleshoot my car tomorrow morning! Thank you🙏

the carb cleaner trick found my leak !! thanks for the tip !!!!! glad I watched your video !

Dude, you're the man!!! I had both codes on and a stupid hose was disconnected! I was about to go nuts.

Many thanks, great the way you take the viewer step by step through the possible faults.

Excellent teaching! I’m glad I finally found this channel!

1A auto you guys are the best all of your videos very comprehensive and easy to follow

Well explained voss!! You were born for this 👍🏻👍🏻

Thanks for this helpful video. I had the P0171 code on my 2019 Colorado, and found a loose hose on the intake. I reconnected the hose, started the engine, and the check engine light was off!

I watched a lot of videos for this error code and yours was the most thorough and helpful, thank you!! :)

yep you were a great help did a oil change and they left the hose unhook. Put it back and it wwas fixed. Thanks a lot

Wow you are amazing! Thanks to you I save money and got rid of my headache, I found a loose hose/vaccim line.

Thanks again for the tips this Chanel saved me a lot of money god bless everyone

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.

Thanks for the heads up, replaced water pump and forgot to reconnect tube into air box creating a P0174, all good thank you

Super!!!. Your delivery is off the hook. Thanks man.

What a revelation video, straight to the point, very clear with hands to work.

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!

Thanks for this video. It's just the right amount of technical, and saved me a lot of effort.

Great video! Right to the point and very helpful, thanks!!

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!

Excellent explanation.God bless you man.it helps a lot.thank you.

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

Very helpful, I had a couple loose vacuum hoses and the airbox not properly sealed.

Just checked my 2012 Honda Civic and found a 5/8" ID hose disconnected and reconnected it with the spring clamp. Hopefully that is enough. Great video!

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.

A man I my light been on for an minute I overlooked ur video after that. I seen no issue in so many other words Thankyou good day.

Just figured mine out! Replaced the injectors and intake manifold. After much headache chasing a vacuum leak, I found my new set of injectors were junk. Could be injectors as a cause of lean code or rich code. My case for lean was the injectors. Didn't want to redo tje intake manifold a 3rd time. Was worried I had a crack in the manifold.

Listen for hissing or use carb cleaner and spay on some areas (hoses or where air flow would be, avoid electronics if possible) while engine is idling to see if the carb cleaner smooths out the idling, if no hiss or no change with idling and carb cleaner, check fuse for O2 sensor (usually under hood), if fuse is good, could still be a bad O2 sensor, if you want to try replacing the first upstream one whichever bank its on (cylinder 1 or cylinder 2 for the banks respectively) can try that route, as its usually cheapest. Harder down the line and more cost involved is fuel rail/fuel injectors, fuel filter and pump, EGR and PCM (Powertrain control module), good luck guys and dont burn yourselves on hot exhaust. Hot exhaust is best and easiest way to remove 02 sensor but its also the most dangerous, so keep that in mind and focus on safety.

Nicely done, a reasonable common sense approach and diagnosis.

It helps. I have P0171 and P0300, the 03 silverado runs very rough when near op temperature, black exhaust and spitting sound as well. Ah modern vehicles, I wonder if I can buy my old Nova SS back, simple reliable and durable. Today's stuff start it wonder when is something going to fail? Then what is it and caused the failure.

Thank You! A hose leading to the snorkel was disconnected! I had Code P0171 and P0174

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.

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. 💰.

Your Suggestions worked. Thanks!

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.

Thank you, your videos are great. In this case, I had a hose disconnected from the filter box, once attached I re checked and it was fine. Thanks again.

My friends Lexus has a torn open hose between the air filter and intake.

I got both of these codes. Im a single woman and appreciate you giving at least some advice for checking before I spend a lot of money with the mechanic. IT COULD BE A SIMPLE FIX!! 🙏🏼🤞I have fairh in God but not necessarily my abilities. He can guide me to the correct issue. Bless you!

Excelente video thanks for sharing

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.

Really appreciate the good work from your tech's😁👍

Good job you show the possibility of po171 but not mentioned how you finally fix the issue

Thanks for the info. I checked the airbox and the snorkel. Mine was loose and after tightening up the bracket and presto the check engine light went off. Thanks for the Info.

Thank you, that was perfect, becouse my car is doing that, so now i know wat to do thank you, big help

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!

Thanks. Mine has scared me twice in 2 years. But it still runs ok.

Thank you for the video

excellent! very complete - THANKS

Another Great video A1 Auto 👌🏾!

What about having excessive fuel additive in the fuel? Will that create the code? Awesome video very informative.

Thanks my car have that problem I will check that and I hope I can fix mi problem.Thank again for your help.

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?

I was getting this code and random stalls on my 03 silhouette. New mass airflow sensor for 30 bucks fixed it.

Thanks Sir this fixed my problem👍

Great video. Now I know how to deal with the shop. I think my problem is in the heater AC vacuum line. This shop replaced the AC control head and ever since then it did not seem to work right and now am getting the PO171 174 system too lean code.

Very informative video thank you very much

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.

That was an excellent video. Thank you.

A 2015 Malibu I have had the check engine light come periodically with the P0171 code and after several trips to the dealership they finally diagnosed it as a faulty fuel pump. After replacing the fuel pump that took care of the problem for a while. But now I notice that I get a check engine light on with P0171 when the outside temp gets down to about 48 or 49 degrees. I took the car into the dealership but they could never find a solution, after several hours they just clear the light and don't charge me anything. The engine always sounds fine and there's no acceleration problem with the light on. At this point, I really think the ECU software may need to be debugged so not to be so picky if mechanics can spend hours and not find anything. The engine is an ECOTEC 2.5L DOHC, 4-CYL DI/W/WT INTAKE WL & AUTO STOP/START.

Great trick. Thank you very much.

Excelente, Thank you

Thank you sir it was so well explained. Very helpful God bless 🙌

Thanks very helpful and nice touch at the end 😂! Any videos on P0300 with others like P0302, 4, 6?

How bad is it to keep driving my 05 chevy cobalt for now until i have someone look at it

Bro, super helpful. Excellent video.

Great video thank you for sharing!!!!

Thanks for the very good information

Just put my transmission back in and am having this code. I noticed I have a small dent on my 02 sensor above the cat. Going to replace that and hope it fixes the issue

nicely explained. thanks

I just wanted to let you know,thank you so much for the video u saved me so much money

Thank You, greatly appreciated your video

Thanks for the information. I really dug your character, Cyrus The Virus in Con Air. Say hi to Nick Cage for me.

Very helpful 👍

Thank you so much. Bless you.