Come along with Eric O. at the SMA shop as we have a look at this Chevy 2500HD with the Duramax Diesel 6.6 LLY that has the famous EGR Code P0401 and P0404. Insufficient EGR Flow and EGR Valve Closed Performance. We run down the diagnostic procedure to diagnose and repair these codes and also flash the ECM with the latest software to make sure it is up to date. The we show the importance of retesting your work and running the monitor.
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50 thoughts on “Chevy lly duramax egr codes p0401, p0404”
  1. Avataaar/Circle Created with python_avatars Kernica1 says:

    if something egr related is bad, can a symptom push coolant back up through the overflow reservoir?

  2. Avataaar/Circle Created with python_avatars Lukas Grincevičius says:

    During first EGR test you've only opened valve to 20%, not 30% . And during second test you've got identical 22g/s when you briefly got it at 20%. MAF cleaning didn't do anything seems to me

  3. Avataaar/Circle Created with python_avatars robert bennett says:

    Hey Eric, Im a fledging DYI want a be. What scan tool do you recommend based upon value and affordability. thanks, Robert

  4. Avataaar/Circle Created with python_avatars Antonio Claudio Michael says:

    Good Repair and Diag Nice work as always Eric O @SouthMainAutoRepairLLC

  5. Avataaar/Circle Created with python_avatars John Plate says:

    I love this channel and I have had the same truck for almost 7 years

  6. Avataaar/Circle Created with python_avatars Michael Price says:

    I am sure those cheap oiled gauze air filters would fail when they fill up with dirt which they do easily. I prefer the stock paper filter. Much easier to replace.

  7. Avataaar/Circle Created with python_avatars Lloyd Kaylor says:

    Would love to see a repair or replacement of a Duramax turbocharger….the variable vane issue…Looks like I may have to fix mine, I refuse to spend the money to replace it. the dealer wants $4,500 for the job!!

  8. Avataaar/Circle Created with python_avatars David g Figueroa says:

    Good job

  9. Avataaar/Circle Created with python_avatars Cobalt Drilling says:

    Hi there awesome video!! I know the thread is older but hoping you still cruise the comments … I have a similar issue with my 2007.5 lmm I replaced the cooler, valve and motor.. will this procedure you did here be considered a re learn? I've read a couple blogs stating I would need a re learn. Any help is appreciated!

  10. Avataaar/Circle Created with python_avatars Gunnar Poe says:

    Its 773.46 I think

  11. Avataaar/Circle Created with python_avatars Gunnar Poe says:

    I don't know how much air weighs. Why isn't air measured in cubic centimeters per second? I guess that's rhetorical. I can't picture a gram of air.

  12. Avataaar/Circle Created with python_avatars George Hauck says:

    I applaud your professionalism. If it was a buddy I’d take him outside and whisper to him “egr blocker and finger stick” and send him a few how-to videos

  13. Avataaar/Circle Created with python_avatars Shane Dirden says:

    I've got a 2004 silverado 195,000 1 belt 1 alternator 1 hub assembly you can have your ford's etc

  14. Avataaar/Circle Created with python_avatars Jeremy Dobson says:

    “ looks like a Chevy salvage yard out here”. Lol haha. Do you see a lot of a certain brand vehicle? (Chevy dodge Ford)

  15. Avataaar/Circle Created with python_avatars Donald Rackley says:

    Great video Mr owe 👍

  16. Avataaar/Circle Created with python_avatars David Dold says:

    Thanks for this vid, stumbled onto you and becoming a fan. Ive got an 05 lly orig owner, living a no-tow, charmed life in San Diego 90k. Not knowing what I would find, and not wanting to clean it… called it maint and replaced with new AC/Delco f/ Amazon. Can you comment on X66P and balance rates? Thanks.

  17. Avataaar/Circle Created with python_avatars R Guy says:

    I removed all that EGR stuff on my LLY. Also replaced the restricted turbo inlet elbow. 😁😁

  18. Avataaar/Circle Created with python_avatars ki6uve says:

    Do you happen to know if the 2003 has the same EGR system as the O4? My local shop cannot seem to get my P1404 code resolved and I would love to point them to this video if it applies. Thanks and great video!!

  19. Avataaar/Circle Created with python_avatars dannyo66 says:

    Working at Walmart as an Auto Care Technician, I have definitely seen much dirtier air filters in diesels.
    Walmart does carry Fram as their filter contractor for air filters, but Fram has 2 levels of filters. 1st is the Fram Extra Guard, their basic filter, and 2nd is the Fram Ultra Synthetic which is their premium air filter.
    When I replace filters, if I know it's going out into the oil patch in North Dakota, or seeing a lot of dirt road usage, and if it's a service type rig, like this one, I'll use the Ultra Synthetic. If it's someones town driver, I'll use the Extra Guard. But I will also offer an option and recommend the Ultra Synthetic for it's better filtration characteristics.
    Walmart just started carrying the Super Tech line of air filters too, but we went into shutdown with the Auto Care Center due to Covid19 right when we got them, so I haven't had a chance to install any or see how they work compared to Fram.
    There are a lot of good air filters out there, stick to a name brand and you'll be fine. (incidentally, AC Delco and Wix/Napa Gold are also good filters, but you never see a comparison between Wix/Napa Gold, K & N, Mobil 1 against a Fram Ultra Synthetic filter. They always compare them to the Fram Extra Guard and poo poo Fram for their inferior filter compared to the other premium branded filters. I wonder why that is……………………….)

  20. Avataaar/Circle Created with python_avatars neal fox says:

    Great job Mr. O!!!

  21. Avataaar/Circle Created with python_avatars Raymond Decaussin says:

    I have an 06 Silverado 3/4 ton with the Duramax. It has 551000 miles. Will the MAF cause the engine to go into limp mode while hauling heavy loads?

  22. Avataaar/Circle Created with python_avatars thomas m. tordel jr. says:

    lol schivvie salvage yard

  23. Avataaar/Circle Created with python_avatars RON OBRIEN says:

    yea Eric, big gaff missing that 20% thing. joke, joke. your skills are truly extraordinary. great result as always. thanks for all your videos.

  24. Avataaar/Circle Created with python_avatars Steve Waclo says:

    When I did injectors on my CA LB7, I discovered a pinched line near the vacuum pump that had been causing an EGR MIL.

    Easy fix.

    Does the LLY have the same EGR system (including cooler) as my LB7?

  25. Avataaar/Circle Created with python_avatars Luis Patino says:

    "This place looks like a chevy salvage yard out here…" 😂😂😂 that's it im going Toyota…

  26. Avataaar/Circle Created with python_avatars Tom Oakhill says:

    This is wonderful. I have wondered for decades how an engine can work. I mean the intake valve is open for less than 1/100th of a second @ 3000 rpm. If the engine is 2 liters than every second it draws 50 liters of air, and that has a mass of 50gms. This has bothered me for years. It is nice to see my math is correct.

  27. Avataaar/Circle Created with python_avatars Robert Kohut says:

    Nice!!

  28. Avataaar/Circle Created with python_avatars Buff Barnaby says:

    iSUZU sure makes good diesels.

  29. Avataaar/Circle Created with python_avatars Paul Bakovic says:

    The air inlet is taped off on the inner fender!?
    For cold mornings?

  30. Avataaar/Circle Created with python_avatars donnie jackson says:

    I loved Mrs.O in your window , like Hello lol

  31. Avataaar/Circle Created with python_avatars M.B says:

    Lol. Chivy salvage yard.

  32. Avataaar/Circle Created with python_avatars James P Bergeron says:

    Going through periodic no throttle, black smoke then sudden clear up, until the next episode. No rhyme or reason. Boy do I wish you lived near me. I'd be on your doorstep begging.

  33. Avataaar/Circle Created with python_avatars A Physics Professor says:

    EGR … thanks eco-nuts. We welcome your shoving of rules up our business.

  34. Avataaar/Circle Created with python_avatars A Physics Professor says:

    Moral of the story … clean your MAF sensor and change your air filter.

  35. Avataaar/Circle Created with python_avatars W KB says:

    Never use break cleaner on a MAF.

  36. Avataaar/Circle Created with python_avatars Jennifer Rae Fuchek says:

    How do you check what programming has been completed for a specific VIN?

  37. Avataaar/Circle Created with python_avatars Atanacio Maldonado says:

    Where are you? I have same problem with my duramax 03 some mechanics trying to find the problem but cannot find the problem is same code p0401 and p0404 the check engine light is on I apréciate if you give me some tips

  38. Avataaar/Circle Created with python_avatars Mike Chiodetti says:

    "Fast And Furious!" Great Video! Mrs. O In the video = icing on the cake! Where's Sheba?
    Learned something new about Duramax EGR and MAF relationship when testing. Great!

  39. Avataaar/Circle Created with python_avatars Kyle Self says:

    I have an 05 LLY and mine is showing the same codes, P0404, P0401cranked this morning and ran for 5 seconds and won’t start
    Changed the air filter and cleaned MAF and still won’t crank. Changed the MAF and still nothing. Batteries good
    Any suggestions?

  40. Avataaar/Circle Created with python_avatars Sting says:

    Delete and live forever

  41. Avataaar/Circle Created with python_avatars Alex Hines says:

    Got me one of those astro worklights and love it. You have had plenty of duramax vids, would like to see some 7.3's . Gotta have some up north.

  42. Avataaar/Circle Created with python_avatars XMG says:

    We got a big shitty here power max 😂

  43. Avataaar/Circle Created with python_avatars Bart fox says:

    I just wanted to say Edsel…lol

  44. Avataaar/Circle Created with python_avatars Cragified says:

    Electronic Engineer myself and my opinion: If the mass airflow sensor cleaner can't clean it then nothing wrong trying some carb or brake clean. You have to replace it it anyway if you can't get it clean and it's not reporting properly.

  45. Avataaar/Circle Created with python_avatars Duncan Mac says:

    Thanks for the video.

  46. Avataaar/Circle Created with python_avatars anthony hager says:

    Love your show always learn

  47. Avataaar/Circle Created with python_avatars anthony hager says:

    Buy a program delete the egr you won't have to worry about it anymore

  48. Avataaar/Circle Created with python_avatars myfastcars says:

    GOD POWERS!!!!!!!!!!!!!!!  You amaze us!  Really,, YOU ROCK!

  49. Avataaar/Circle Created with python_avatars John Ferguson says:

    Mama telling you to stop playing with your truck and get back to work … Life with three kids to feed. You made em, now you've got to feed em.

  50. Avataaar/Circle Created with python_avatars Sam Rugtiv says:

    Good job Eric, I always use b 12 seems to work good also. Sam

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