Chevy GMC Code P0172
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- Опубликовано: 17 окт 2024
- In this video we discuss the most common cause of a GMC or Chevy flex fuel equipped vehicle with a check engine light illuminated and a stored code P0172. These GM produced Flex Fuel systems use a PCM based virtual flex fuel sensor (V-FFS)algorithm in order to calculate fuel metering. The ethanol level calculation occurs with the engine running after a refueling event has been detected via a measured change in the fuel level sender output. The V-FFS algorithm temporarily closes the canister purge valve for a few seconds and monitors information from the closed loop fuel trim system to calculate the ethanol content. This logic executes several times until the ethanol calculation is deemed to be stable. This can take several minutes under low fuel flow conditions such as idle, or a shorter time during higher fuel flow, off-idle conditions. Earlier PCM software versions tend to error on the side of higher fuel alcohol content over time requiring a reset of those learned values to bring LT fuel trims into range. Watch this helpful video for more information.
We mentioned a video outlining testing for verifying fuel alcohol percentage. Watch that video here: • How to Test the Alcoho...
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I like the little slower more modulated pace of your instructional delivery in this vid. Makes it easier for my aging brain to absorb what you are saying. I don't want to miss a word.
I know all about slow brain absorption; It seems like I also suffer from loss of brain retention. Thanks for the positive feedback and its always good to have you drop by. Take care.
Thank You Sir, Your video helped me. I really didn't understand what p0172 meant. I noticed the in my scanner the long term fuel trim was -26.99%. After reviewing your video I saw the alcohol content was 76%. After the fuel composition relearn, and resting the fuel trim data and spraying the mass air flow sensor with the proper spray. I cleared the code and the car started normally. No parts needed. Thank You again.
Now that's a condition that could throw you on an expensive parts buying expedition. It's nice to see tips like this on your channel, thanks for showing these tips of the trade. Awesome Tim 👍👍🍺🍺
Dang car went out drinking without me.
Thanks brother. Oh, I think people know by now anyway so I might as well say that your my twin brother. Born ten minutes after me. I decided to naturalize and become a US citizen but you stayed in the homeland and have done well for yourself. Give the rest of the family my love.
Yes, I spent $700.00 on parts I didn't need because the mechanic didn't have the software to reset it. He should have tested the alcohol content which would have told him the computer was reading it wrong at 50% as the fuel in RI is only 10% or less ethenol.
My percentage was at 50%. Reset and it went back to 10% and fuel trims came back to zero.
Thanks for the help.
FYI, my snap-on Solus ultra did not have a data pid for alcohol content. The only way I could see it was when I reset it, there was a data pid on the reset screen.
This video was 'just what the doctor ordered ' for my 2009 impala. Thanks
This is why I am hunting for a classic. Screw all this EPA bullshit.. Sensors for this.. sensors for that... Geez! By the time I'm done putting all this money into this BS I could have run a 57 Chrysler for FAR way cheaper and Farther! Just another form of Slavery to keep us spending and for what?! Now as for this video 2 Thumbs Up!! I thank you sir for your knowledge. I live where sand storms and dust is a way of life and I don't have time to go out and buy sensor after sensor just because the wind picked up. Love the Video, hate the Gov't forced upon us BS.
Keep crying.
If anyone can tell me, my question is what causes the alcohol and fuel trims to need to be reset, bad fuel fill up and the pcm doesn’t re learn it’s values once filled up again? I spent hours trying to diag this code and this video saved me a lot of time. But I’d like to know why it does this to begin with?
The updated flash for pcm modifies how alcohol percentage is calculated and is the long term fix. Inaccurate calculations as result of faulty sensors and poor programming cause the learned values to climb to levels that create inaccurate fuel to air ratios and poor performance.
Thanks for the help Tim! I had this 09 hhr 2.4 flex fuel driving me crazy for a couple of hours today at work! Following the flow chart per Mitchell and I kept coming to a dead end as every part checked out, I.e fuel pump, fuel injectors, evap system, no vaccum leaks, no clogged/dirty air filter assembly. Fuel was reading at 75. Reset both values and now I’m reading a total of 1-3 correction at idle!
Thats odd. I have the p0172 also, and the alcohol % is 75% also.
I just got this code on my 08 impala few days ago. I have a basic cheap handheld scanner that reads codes clears them and minor things. I dont have a option to clear or reset the fuel trim. Can I reset the fuel trim by unhooking the battery 5min? I erased the code but the check engine light came back on 10min later. I'll clean the maf sensor tomorrow. Also what is bank 1? Is that the front 3 cylinders of the engine? Thanks for the video.
Good video Tim and right to the point!
Thanks for the encouragement and support!
Will a bad map sensor turn the p0172 code? I replaced air filter and cleaned the throttle and i recently replaced fuel injectors.
Could you post some scan tools that will clear these codes?
My 2008 chevy imPala just gave me this code ill start frm there thanks for video ✌
Era at system
Era wysystems
Erq wt systems
What if I have the same code on my 2014 Silverado xlt?
I replaced both o2 sensors upstream and downstream with stock denso sensors from rock auto. Th e sensor on the cat furthest from engine wouldn't come out so I heated it cherry red with a torch, I removed the sensor and all the threads were distorted stripped. then when I went to thread in new o2 sensor it wouldn't thread in due to the threads were damaged. I crossed threaded the new sensor it because I've had enough. . I'll get someone to weld it I guess one of these days. I have No drivability or misfires car rides idles accelerates smooth with no hiccups. I cleaned the mass air flow erased engine light with my cheap scanner.. But light comes back on few min later. Any ideas where or what I should check next. I cant check fuel trim or alcohol content of fuel. Is there a scanner in 300$ or less range I could buy or am I outta luck. Also how do I check vacuum leaks with carb cleaner?
Check out the blue driver scan tool
Hi Tim, This was a very helpful Video, Thanks.
I was just wondering since we put that HEET in our gas during the winter here maybe that can lead to this issue. Interesting stuff to ponder. Thanks for dropping by.
I have a 2008 Impala LT Flex Fuel. I was running on empty and then when I refueled it triggered a Fuel Composition Relearn. It relearned it at the wrong composition amount causing my Check Engine Light to come on. Code P0172 system too rich. Needed a Fuel Alcohol Content reset.
Do you reset it with engine running
@@turbot6592 I had to bring it to the dealer to reset the alcohol content on the computer. My system was saying my fuel was 50% alcohol. They tested the fuel and it was only 8% alcohol. They had to reset it to the correct reading. The software you need to do this is probably only available at the dealership as it is too expensive for the average mechanic.
I have a 03 S10 2.2 it was running lean code p0171 , put a fuel filter on it and all was well for a couple days , now I have a P0172 rich code , could you give me an idea of what would cause it to go from lean to rich , I'm old school mechanic trying to learn these sensors , thanks man , great video👍👍👍
wow, my alcohol content is at 55%. Guess Ill start there. THANKS.
Good info as usual Tim. Thanks.
Thank you sir
Good tips Tim !
Because cool viewers like you should get cool tips! Blessings.
I chevy impala 08 I have code p0172 how can I fix it
Would adding things like fuel anti freeze cause these trims to change. I put a small bottle in my tank during the winter when I know the temperature is going to go below -4F or -20C. I can't say I have experienced a problem doing this, but then again my van is flex fuel capable. Thanks for the vid Tim I'll see ya later buddy. -John
This problem seems with the GM virtual flex fuel sensor vehicles and not those equipped with actual fuel alcohol sensors like many trucks and vans. Not sure of your configuration or latest PCM flash. Thanks for dropping by.
Great information. Thanks
Thank you!
exact code I needed aid with!
Great vid.
Oh wow, well then this video achieved my goal of helping someone. Hope you get yours fixed up.
does the same go for bank 2 fuel trim
P0175?
Whats your year, make model and engine size? Is it a flex fuel engine? Have you looked at fuel trims?
Never have.
I believe it is a 325 ci
flex
07 tahoe
I'm no expert, guilty, where could I find that certain number on the block engine to determine ci size ? hope you'll get back to me on that c:
(>^.^)>
OH, I would guess MAF problems or leaking intake gaskets. Have you done intake gaskets yet?
Good video. Thanks for sharing. Thumbs up my friend.
Love the thumbs up!
Fantastic info Tim. Flex fuel vehicles aren't too common round here
Seems like they have a lot of issues around the use of those fuels. It also sounds like it costs more to make the E85 fuels then regular gas but here the government pays farmers a subsidy to grow corn and sell it for less. Then we pay more for meat because they have to charge more for feed since there is a premium on corn. We live in strange times.
over here we make fuel from the waste products of the beer brewing process. it's called brewtroleum. everyone's a winner
We make fuel from french fry oil here and I do my part to help the environment every time I visit the fast food restaurant.
This is great information Tim. We can at least be informed customers if we don't have a scanner. :)
I'm learning right along with you buddy. I might have to get some of those graduated cylinders and try the fuel alcohol test. Cool stuff.
Thank you
Thanks for the info Tim...as always great video!! THX
Thank you!
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Most of our fuel in Canada has 10% alcohol accept for Shell 92 octane. That's all will use in my small engines.
Wow, I had no idea how much alcohol was a problem across the globe.
No alcohol in the fuel, isn't ethanol alcohol. All our gas in Alberta has that in it. Up to a couple years ago all the pumps had stick that said 10% ethanol, but now most gas has like 25%, that's why we need to use iridium spark plugs, so they don't burn up.
No we don't have ethanol in our gas here. Not sure about the rest of the USA. I was thinking that we do sometimes use HEET gasoline antifreeze so that can contribute to alcohol percentage.
I do think I am sadly ignorant in regards to ethanol fuels and even the flex fuel system here. I know this is a common problem and that's why I made the video. I also know that doing the relearn fixes the problem at least for an extended period of time but the reflash is more of a permenant repair. That said I believe you are correct about higher percentage in current ethanol fuels. I wasn't aware of that since like I had said we don't have any in our gas. I'm glad too because it sounds like you get crappy mileage with that stuff. Lame.
The Car Doctor I think in some cases we don't get worse mileage, but, its been said that the newer vehicles, last few years fun better on it. And like I said about the iridium spark plugs, the older vehicles need them to run better on the stuff. The regular platinum plugs that say your supposed to get 100 000kms before you have to change them only last maybe 50k before the tips are burnt off from the ethanol.
Why only 06-2010 done 11-12-13 use the same algorithm?
The published TSB regarding this indicates the later production dates had updated software but im only going off what I read. Do you have and published documents showing where this information isn't correct? I would certainly consider updating the description to correct any false information. Thanks for the feedback. Take care
I do not. I just know mine is a 2011 and I had to have mine updated for alcohol content.. at least that's what I was told.by the dealer
I just don't understand why when you fill up the next tank of gas why it won't readjust by itself
You were sounding more like a tv advert by the end lol, you should of added,
"Get my Essential Expert Guide to car repairs Now!!, Only $19.95 at all good outlets." LOL :-D.
I did see something last year to do with adding water to petrol and the alcohol attracts water, so it forms a layer at the bottom of an old drinking glass, or something like that.
Alcohol attracting water, sounds like bad news for a fuel system :-(.
Up here we use an additive called HEET to prevent fuel systems from freezing. It's really just a bottle of alcohol. The ISO HEET is made from isopropyl alcohol and actually absorbs water and removes it from your fuel system. I think over time the E85 fuels will do the same thing since they absorb the water that's naturally in your tank due to condensation and atmosphere humidity. But I'm not a scientist so don't take my word for it. I'm just a TV announcer. Hehe
Can a normal gas engine run on this E fuel ?
I think so but not as efficiently. I know that some small engines can burn up if you use those fuels in them. I wouldn't suggest using it in a non-flex fuel vehicle.
You do this while the car is running. Reset it
Aaaargh, next year E10 fuel is coming to Belgium :(
I'm driving a 30 year old carbureted car, hoping it'll be fine...
It'll be fine after you have replaced all the seals, gaskets and hoses dissolved by the alcohol. Of course your mileage will also be reduced.
hahaha sad
Just keep a close watch on any rubber fuel lines as alcohol will eat them for breakfast.
Next thing you know a flag is going to be raised on the car so the cops can see the car is inebriated.
Sir I pulled you over because your engine is staggering
:> )
How is any video that only tells you how to fix something if you have a scan tool helpful to the do it yourselfers? And who else is watching RUclips videos on auto repair other than don't yourselfers?
I felt like this was good info if anything else. There are lots of cheap scantools that can help you with this sort of issue and many DIY folks are using them to save big bucks. Also the info here could save you a lot of cash even without the use of a scanner. Or you can just take it to a shop that has the equipment and pay them.
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احسنت
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scripted speaking??
No, just did about 100 retakes of each sentence. I was considering scripting it but didn't. I wanted to sound professional. Did it sound that way?
sounded scripted. but the content was good
My usual video includes a lot of "ahhh, ummm, ahhh" and so on. My brain just doesn't seem to function like it used to. It's a struggle to piece together coherent sentences sometimes especially while filming. Too much LDS in the 60's 😀
Great Star Trek 4 reference! Me Too!
phil holbrook l,