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In this video Miss Marie has a look at a Chevy Sonic that comes in with the engine light on and has a lean code stored in it. This is her first diagnosis she has attempted and is an ambitious learner! Be sure to check out Mike over at NGK to learn more about Fuel Trims and up your game when it comes to lean and rich codes. -Enjoy!
Fuel Trimsโ€”Testing & Diagnosing Rich and Lean Conditions (P0171, P0172, P0174, P0175): https://www.youtube.com/watch?v=BlcWBZ-iaTY

49 thoughts on “Chevy sonic: running lean p0171 – part i”
  1. Avataaar/Circle Created with python_avatars Morr Sey says:

    I like your time

  2. Avataaar/Circle Created with python_avatars Morr Sey says:

    I like to work with you

  3. Avataaar/Circle Created with python_avatars Charlie Yuson says:

    same problem in my car P0171 but the dealer said it is my turbo but it seems i dont believe in now i watch a lot youtube about lean but nobody said the turbo is the cause thank you

  4. Avataaar/Circle Created with python_avatars Profi says:

    We didnโ€™t understand what was the problem, what part you need to change to fix that??

  5. Avataaar/Circle Created with python_avatars mrnoobzoo says:

    Another one to note before confirming fuel trim data is if the fuel trim is in closed loop. Great info guys

  6. Avataaar/Circle Created with python_avatars twwtb says:

    Learn by doing is exactly right. I'm 3 times your age and still just learning about these codes and 'puter gizmos on my cars.

  7. Avataaar/Circle Created with python_avatars ื ื—ืžืŸ says:

    eric hi i think its regulator diaphragm and not pcv valve tell me if i correct

  8. Avataaar/Circle Created with python_avatars Mark Ash says:

    excellent video Marie. Great job and thanks for sharing!

  9. Avataaar/Circle Created with python_avatars sostok says:

    guru on the scan tool. great work Marie.

  10. Avataaar/Circle Created with python_avatars hightttech says:

    Definitely a SOLID joke ๐Ÿ‘

  11. Avataaar/Circle Created with python_avatars Hola! Tom Berry says:

    seems like minded is doing the same thing but has not trip the engine light on so I can put my scanner in her. 170.00 for a valve cover from the dealer grrrr

  12. Avataaar/Circle Created with python_avatars Bymmijprime says:

    Awesome video, thanks!

  13. Avataaar/Circle Created with python_avatars R Barndt says:

    Miss Marie,
    I am very impressed. It appears that you retain what you learn and can apply it to the diagnosis at hand. Keep up the good work.

  14. Avataaar/Circle Created with python_avatars Salah Bona says:

    Pvc valve stake open

  15. Avataaar/Circle Created with python_avatars Sean McGuirk says:

    The young woman is very fortunate to have an honest and good teacher of diagnostics.

  16. Avataaar/Circle Created with python_avatars Daniel Wirtz says:

    Stoichiometry, and y'all didn't think you would use chemistry after high school.

  17. Avataaar/Circle Created with python_avatars Cande Ramirez says:

    What if I changed my freshair intake hose and it still shows me the check engine light on?

  18. Avataaar/Circle Created with python_avatars Alexia S. says:

    good job guys

  19. Avataaar/Circle Created with python_avatars Phill Spunt says:

    Hey I have a 13 Sonic lt with the same code, I had it come up last week and it shut back off, now it came on again. Any thoughts on what that may be?

  20. Avataaar/Circle Created with python_avatars Yammie Tom ogrady says:

    Good Job… Lots of info on the Echo Tech. I have one in my Wave.

  21. Avataaar/Circle Created with python_avatars Efrem Williams says:

    Love when you work with Marie. I learn along with her. Great video

  22. Avataaar/Circle Created with python_avatars We Are Anonymous says:

    Hate this code

  23. Avataaar/Circle Created with python_avatars Erin Sherman says:

    Can someone explain why the engine stalled when the dipstick was removed? I understand what the PCV does and how this failed valve is causing negative pressure in the crankcase, but why does relieving that pressure cause a stall? Is there a sudden additional inrush of (unmetered) air and the ECU just canโ€™t change the fuel trims fast enough so the mixture becomes so lean that it wonโ€™t ignite?

  24. Avataaar/Circle Created with python_avatars V Star 1300 Adventures says:

    Dealing with that stupid code right now on my 2014 Sonic LT.

  25. Avataaar/Circle Created with python_avatars Steven Ybarra says:

    Would powertrain warranty cover this?

  26. Avataaar/Circle Created with python_avatars Marco Philhom says:

    What scan tool are you using. I like how the fuel trim numbers are presented.

  27. Avataaar/Circle Created with python_avatars Bill Scott says:

    Thank you Marie and Eric. My 2012 Chevy Malibu was showing few vac leaks. Just replace my oil filler cap on my engine. Learn a few things from the video.

  28. Avataaar/Circle Created with python_avatars Jeff Mitchell says:

    This sucks, I'm out of here.

  29. Avataaar/Circle Created with python_avatars John M says:

    Classic locked hood technology. PCV valve built into the valve cover. The Diaphragm is torn

  30. Avataaar/Circle Created with python_avatars CASTLEDOME KNIVES says:

    Young lady is smarter than most YT mechanics

  31. Avataaar/Circle Created with python_avatars Kevin Berg says:

    Not to be overly nitpicky, but when you rev up the engine under no load, the reason the fuel trims improve when there is a vacuum leak is because the overall airflow into the engine increases while the amount of air getting in through a vacuum leak stays roughly the same, therefore the fuel trims improve because the vacuum leak is causing a lower percentage of error in the MAFS reading. For example, lets say you have a vacuum leak that is allowing 1 g/s of unmetered air in on a 2.0L engine at 20 inHg, where we might expect to see 2 g/s of airflow through the MAFS under normal conditions, the vacuum leak will be causing a 50% error in the MAFS reading, so we might expect to see total fuel trims around 50%. If we increase the engine speed off idle to 3000rpm, we may see the airflow through the MAFS increase the 5 g/s under normal conditions, but because the manifold vacuum is not significantly changed by revving the engine under no load (I'd expect almost no change once the engine speed levels off, it may even increase manifold vacuum due to the higher engine speed) the vacuum leak will still only be allowing in about 1 g/s of air. So, that 1 g/s of air caused a 50% error in the MAFS at idle when the engine is ingesting 2 g/s of air, but its only a 20% error when at 3000rpm under no load when the engine is ingesting 5 g/s of air, so the total fuel trims should improve to around 20%.

    Great job with the video and teaching a new tech how to properly diagnose a car.

  32. Avataaar/Circle Created with python_avatars James Washer says:

    Nice job Miss Marie. I hope you are doing well and still working on cars. Waiting for the MMA (Miss Marie Auto) channel!

  33. Avataaar/Circle Created with python_avatars Jeannette Aviles says:

    It would be cool if you can do a timing belt change on one of these bad boys

  34. Avataaar/Circle Created with python_avatars CD'S Automotive Garage says:

    Dangg why does gm or anything change a simple tool or part that did just fine with a pcv valve outside on the valve cover that pops in and u just change that when they fail instead of this crap built in . All this is , is a money racket bs they always gotta do something. ๐Ÿคฆโ€โ™‚๏ธ๐Ÿ™„ gezzz just dumb engineering

  35. Avataaar/Circle Created with python_avatars Neal Null says:

    Way to go miss marie its awesome to see the younger generation learning to work on vehicles

  36. Avataaar/Circle Created with python_avatars Sean John022992 says:

    great job!

  37. Avataaar/Circle Created with python_avatars Camby Diagnostics says:

    โ–„โ–€โ–„โ–€โ–„โ–€โ–„โ–€โ–„โ–ˆโ–“โ–’โ–‘ Great job. Keep it going, You will gain an enormous amount of knownedge from youtube Good & Bad, It's knowing which is which that is key. You have a thirst for knowledge, and Eric has it all to share, as long as you have the hunger to learn, Eric will keep you on the right track…… Thank You.โ–‘โ–’โ–“โ–ˆโ–„โ–€โ–„โ–€โ–„โ–€โ–„โ–€โ–„โ–€

  38. Avataaar/Circle Created with python_avatars Slik Rhodez says:

    Great job, Ms. Marie!! I'm so glad to see young people interested in the automotive service field! And thanks for letting us follow along!!

  39. Avataaar/Circle Created with python_avatars and Chips says:

    Well done Marie, keep up the great work ๐Ÿ™‚

  40. Avataaar/Circle Created with python_avatars Neil Howe says:

    miss maries well on her way to her own channel……!

  41. Avataaar/Circle Created with python_avatars ivan drago says:

    Who can give dislike๐Ÿ˜ ๐Ÿ˜ 

  42. Avataaar/Circle Created with python_avatars Lyle Bud says:

    Great Video!