Come along with Eric O. at the SMA shop as he has a look at this 2006 Chevrolet Silverado Flex Fuel with the engine light on and codes P0172 and P0175 Rich on Bank One and Rich On Bank 2. While this code can be a lot of different things the first thing you need to look at on this vintage GM is the Alcohol % Data PID. Also we make sure that the vehicle has the most up to date software from GM.
Important: The system is initialized by baselining itself on ASTM spec Gasoline (alcohol 0–10%). When an E85 compatible vehicle is built, an ECM or PCM replaced, or if the learned alcohol content has been reset with a scan tool, the fuel system will need to contain ASTM spec gasoline with 10% or less ethanol content. If the fuel in the fuel system needs to be drained and replaced with ASTM spec gasoline, the vehicle will need to run for approximately 11 km (7 mi) at full operating temperature before the system will be fully adjusted to the correct alcohol content. Once system initialization has been completed and the calibration verified to be the below listed calibration part number or later, gasoline with any ethanol content between 0 and 85% may be added, provided it is added in a quantity of 11 Liters (3 gallons) or more, and the vehicle is run long enough to learn the new fuel
After the re-fueling event, the system registers the amount of fuel that was taken on-board, relative to the amount that was in the tank. Reading fuel trim and O2 sensor activity, the system determines the ethanol content of the fuel that was added. Based on that determination, it adjusts itself to the expected alcohol mix in the fuel tank and lets the fuel trim and O2 sensor activity fine tune the adjustments. The system must remain in closed loop in order for this adjustment to occur. Numerous short trips after switching from gasoline to E85, or vice versa, can result in driveability symptoms due to the inability of the system to adjust for fuel composition (by not attaining the parameters necessary to reach closed loop operation)
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50 thoughts on “Chevrolet silverado – p0172 p0175 running rich”
  1. Avataaar/Circle Created with python_avatars GTR KoN says:

    That GM system does NOT sound smart at all 🤣 imo. Maybe they need to go back to or get the Alcohol Content sensor's instead of guess work. Wonder why the 02 sensor's don't have the ability to quickly report data back on a rich fuel mixture, then PCM proceed to instantly pull back fuel trims. Rather confusing system that's for sure. Maybe I need to learn more about it perhaps idk 🤔

  2. Avataaar/Circle Created with python_avatars Fridgebuzz says:

    About a month ago I had about half a tank and filled the rest with E85 just to see how it ran. Ever since I've been filling up at either 3/4 or 1/2 tank with regular 87. Yesterday I just got these codes. I'm thinking I need to run until empty, unplug the battery for a bit and then refill with regular since I don't have access to a scanner?

  3. Avataaar/Circle Created with python_avatars Antoneio Dienno says:

    Anybody else have this issue and it not be the alcohol content ? I have a 07 tahoe got a cold air intake and dual exhausts and it use happen pretty often then i tuned it for more hp and better mpg and it pretty much stopped for about a month just got outta work and mid driving on my way home it popped back up i have no vacume leaks my alcohol is perfect fuel trims look great shits driving me nuts lol

  4. Avataaar/Circle Created with python_avatars Patrick Lions says:

    You are a really good! So, the repair was to allow the computer to recalibrate the alcohol fuel % content? By driving it atleast 7 miles or fueling the truck more than 3 gallons. You checked the that the fuel was infact regular fuel. My truck was at 67%. I drove it 20 miles it said 58%. I topped it off (3.8 gallons of reular non e85 fuel) and its came back at 55%. My fuel trims are lovely exept once in a while you get deeper into the throttle the trims go -30, running rich. Same thing though, cel lights on for 0175 & 0172 with computer miscalculating the alchol %. Its a 2013, im guessing its got the latest software for flex fuel but im not sure my computer will read that, ill search tomorow.

  5. Avataaar/Circle Created with python_avatars Patrick Lions says:

    Mine says 62% alcohol 😆, not possible

  6. Avataaar/Circle Created with python_avatars Patrick Lions says:

    Plugged in my scanner and exactly whats going on with my rig. 2013 avalanche 5.3 flex fuel, i suspected something with the fuel theyre selling lately. Mine says 62% alchol, lol

  7. Avataaar/Circle Created with python_avatars BJ Perez says:

    Thank you for the information, I am certain this is the issue with my 2006 Avalanche w/ 5.3. Does anyone know how to solve this without a fancy scan tool or do you need to bite the bullet and go to a shop to have them see if the ECM needs to be reset or reflashed? Thanks in advance!

  8. Avataaar/Circle Created with python_avatars BUDGET BASSHEADS LDO says:

    Amazing! I didn’t even know my 2005 was flex fuel but their was a sticker on the gas cap and every time I would go to the gas pump I would think could it be true? Then I did a little research and found out that if a certain number of the vin is a Z it is flex fuel but it was a Z it was correct. I took it to about 3 main Auto parts store and they ran the vin in the system for my fuel filter they gave me the flex fuel one. One time this kid at O’Reilys gave me a regular one and they didn’t know why it could be. I put half a tank of E-85 and the next day if was running funny. Also I had a diode go bad on my stock alternator so I was going to buy a new battery since it would drain it over two days as well as alternator.Long story short my son bought me a 160 amp don’t what brand from Amazon. It was good for about 2 months. It fluctuates from 15V-13.4 to the 14s and I know just from what I learn in college in dc/ac circuits it to mess up everything. Because it needs a steady flow of electricity. Right? Sorry for the long novel I left here but your videos I will watch for sure. Thanks god bless!

  9. Avataaar/Circle Created with python_avatars Simon flores says:

    Don't have the composition reset function can i disconnect the battery to clear the

  10. Avataaar/Circle Created with python_avatars Ernest beware says:

    I really need help please call me when you get this I don't want to put my number on here but m desperate 830-491-0112

  11. Avataaar/Circle Created with python_avatars FreezurBurnt says:

    Got p0172 and p0175 code, what's the cost to get the reflash,?

  12. Avataaar/Circle Created with python_avatars Francisco Figueroa says:

    Which autel is this? Looking for one I can use to do the reset myself

  13. Avataaar/Circle Created with python_avatars Francisco Figueroa says:

    Would you mind telling me what programmer that is. Looks very useful to a do it yourselfer.

  14. Avataaar/Circle Created with python_avatars Flawed Offroad says:

    Would a 2009 have an alcohol sensor? and do you need a scan tool to reset the alcohol % or is there another way to do it?

  15. Avataaar/Circle Created with python_avatars Rob Thomas says:

    Thank you so much for your help on this vid, exact problem I was having..great content as usual

  16. Avataaar/Circle Created with python_avatars jay ahmadi says:

    I have a 2010 5.3 Sierra Flex and I am getting a p2196 code. I've looked up everything possible and can't find a solution. I have changed the O2 sensor pre cat on bank 1 since the code popped up. New MAF.. No luck….any advice?

  17. Avataaar/Circle Created with python_avatars mike hall says:

    I have an 07 impala ss 5.3 getting bank 1 rich and sometimes I get bank 1 lean codes any idea what could cause that?

  18. Avataaar/Circle Created with python_avatars Shane Chesner says:

    I’m having this issue I did the reset and it made it about the 7 mile relearn the light came back on is there anything else I can do

  19. Avataaar/Circle Created with python_avatars AReal handyman says:

    Mine says fuel type meth and I do have idle issues when I exit the free way runs rich a little of popping

  20. Avataaar/Circle Created with python_avatars Franks Garage says:

    Had to come back and leave a comment. Mr O, thank you very much on the tutorial. After watching this i had to go to shop and check if my problem matched your diagnosis, which it did. 60% is what scan tool showed. Reset it and fuel trim just like you did. I have been chasing this for a while. I can almost guaranfrickentee the lady was nickel and diming the gas tank.
    This 2012 would not start in a warm shop. Will know in the morning. But so far the prognosis is good. And i will be able to sleep tonight.
    By the way,with all the difficult diagnostics , how do you get any sleep? My brain never seems to shut up at night, all the personalities talk among themselves, drove me crazy.
    Gave you a shout out on my channel,sharing what i learned from you…

  21. Avataaar/Circle Created with python_avatars Manthony says:

    Awesome video with incredible information. I love how thorough you are 10/10

  22. Avataaar/Circle Created with python_avatars gordo SR says:

    Hi i have a 2012 GMC Sierra 2500 with 6.0 flex fuel moter ,i have to bring truck in to reset Al hole mixture,after about 2 weeks you start it up and moter is jumping all over then it clears out and runs great all day,engine light comes up,i check the code,and it is po175 ,cant figure out what it is ,i bring it back in he clears code adjusts the mixture and the same thing happens again 2 weeks later,do you have any insight on this it would be helpful, thank you

  23. Avataaar/Circle Created with python_avatars Iaroslav Zubchenko says:


  24. Avataaar/Circle Created with python_avatars Jayj B says:

    I have a rich code and traction control light !!! Car running then try’s to die and back up !!! Just changed cam

  25. Avataaar/Circle Created with python_avatars Jeff Nunley says:

    So what was the problem

  26. Avataaar/Circle Created with python_avatars David W says:

    WOW you have no idea the grief you've saved me. I even use an Autel like yours, I chased my tail a little on this one for an hour or so until I found your clip. subscribed! keep these types of videos coming buddy!

  27. Avataaar/Circle Created with python_avatars John B says:

    What’s the details on the programmer? I know autel makes some but I want to get one that is as easy to use as this one.

  28. Avataaar/Circle Created with python_avatars Ping Pong says:

    Can Torque Pro app reset the alcohol reading? That is all I have access to right now.

  29. Avataaar/Circle Created with python_avatars Ping Pong says:

    Same issue on Pontiac Montana SV6 – dealer updated firmware, reset alcohol and it worked good for a a few days. Then the check engine light came back on, with same problem. Seems the alcohol learning is messed up on these flex engines. They said to use a certain gas station, but how practical is that? I read somewhere that the egr port gets blocked and maybe cause of fuel rich, but I have no idea on that… really lost on this one.

  30. Avataaar/Circle Created with python_avatars R L says:

    Money light is right. I paid $400 to the dealer to correct this. Is there a obd2 that can do this that doesn't cost thousands?

  31. Avataaar/Circle Created with python_avatars CubNole says:

    I may be dealing with this on a friend’s Malibu. He had a P0010 and an open intake cam actuator solenoid, so I replaced that. Also had a timing code and this P0172, none of which have returned but I’m worried the P0172 will be back

  32. Avataaar/Circle Created with python_avatars Chris Lincoln says:

    Great video. I just ordered an Autel and I'm getting the two same codes. I hoping the unit I ordered (MK808BT) will do what yours does. Thanks for the video.

  33. Avataaar/Circle Created with python_avatars kyzercube _ says:

    " coagulate " hehe. I believe it's referred to as going into solution.

  34. Avataaar/Circle Created with python_avatars Keith Hiebert says:

    I just want to thank you for giving me direction on fixing my brothers 2011 Silverado Flex Fuel 5.3 Litre. Long term fuel trim was -26.6 Bank 1, and -28.5 on Bank 2. Alcohol % was at 63.5%.
    Thank you. Truck going to GM for a reflash in the morning.

  35. Avataaar/Circle Created with python_avatars Kenneth Franklin says:

    Actually, you are definitely being a scientists in this video. What a great science lesson.

  36. Avataaar/Circle Created with python_avatars Allen Toma says:

    What scan tool is this?

  37. Avataaar/Circle Created with python_avatars Shawn Swnh says:

    I have these two codes on my 02 Chevy Silverado but it’s not a flex Fuel truck what should I start with? 🤦🏻‍♂️🤷🏻‍♂️😢

  38. Avataaar/Circle Created with python_avatars Kevin Stoffers says:

    Thanks for helping me out

  39. Avataaar/Circle Created with python_avatars Brad Roheliersr says:

    What kind of scanner are you using to reset the alcohol content

  40. Avataaar/Circle Created with python_avatars Andork Kuomo says:

    Damn, that was pretty fascinating!! My '06 Avalanche likes to throw those codes every year or so, I just clear them! Before I start parts changing I should take the hour's ride down and see you first, I'm due north of you up by the big lake! Do I have to bring ice cream or something?

  41. Avataaar/Circle Created with python_avatars Bart says:

    P1174,P1175,P2270, P0109 all together 4 codes.

  42. Avataaar/Circle Created with python_avatars Jahliee L.E says:

    Good noon eric. I have a 2003 chevy suburban z71 ,5.3. With a P0175 ,both long term fuel are at -15% too rich bank 2. What should i look for. Recently i replaced injectors, fuel pressure regulator and the fuel sensor thats on top rear of the engine, when taking out the top cover. I cant recall the name of it. Any info will help.thx