In this video I have a look at a GMC 1500 4.8 with the Flex Fuel engine and according to scan data it is running rich… REALLY Rich! Pretty common issue with these vehicles and it is a really simple fix. So if you have a P0172 and P0175 be sure to check the alcohol composition first.
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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This guy is good!
Binge time with great videos
The problem is, these GM computers don't actually measure the ethanol content of the fuel. It relies on the fuel trim readings to adjust. A real flex fuel vehicle should have a true alcohol sensor.
This would NOT apply to the L96 6.0 correct?
Hi great video. Question: so what is the long term fix for this issue? I have a 2011 flex 5.3 and light comes back after some time. And definitely not running E85. Here in Texas pumps say less than 10%
Question, I have a 2013 gmc sierra 2500hd 6.0l w/ L96 flex engine. I had same codes as this video. Fuel alcohol content was 64%. I was able to reset my fuel trims and fuel alcohol content but I'm still getting the same codes. I have replaced O2 sensors, fuel injectors, and MAF sensor because it threw a code for that. What else could be causing these issues? I'm LOST! Lol
I've had 3 different shops "reset"/"reprogram" my truck, and it's still messed up. I've paid over $500 now, and no one can seem to figure it out. I had 19 codes on my cheap code reader, and the shops won't tell me anything exactly. I feel like I'm just being ripped off. My truck runs great, starts great, and the only time I have a problem is when im accelerating to highway speeds. When I reach 45mph, the truck will stop accelerating, and the check engine light will blink, and the rpms will go up, but the truck just hesitates and stops accelerating. Then I can back off and slowly accelerate to 60mph. Sometimes it doesn't do it at all. All O2 sensors have been replaced twice. MAF Sensor has been replaced twice. Spark plugs twice. Coil packs, half were changed once, and I replaced them all this last time. I got the truck 2 months ago and since then 2 exhaust manifold bolts have broken. They weren't broken initially this was found 2 weeks ago. I'm not sure if this is the issue or a possible issue. The O2 sensors are saying something about heat signal or something. It's only the driver side on that issue, bank 1. On my cheap code reader. If you have time, I can email you a list of the codes I'm getting. I'm in northern Ohio just west of Cleveland. I'd be willing to drive to you in the next month or so if you could help fix my problems. I'm just looking for an honest mechanic that will help me get it figured out. I'm not looking for anything for free , I just need help and I can't find a trustworthy mechanic locally to help me get it figured out. Thanks I appreciate it either way. It's a 2011 chevy silverado 1500 automatic 4.8 L 4×4 with the manual shifter. My email is Bobsnagg123@yahoo.com
I'm not a scammer or some crazy person. I watch alot of your videos and know you take pride in your work and always seem to figure out these crazy issue. My alcohol percentage was in the 40% range and trims were in the 30s. I snuck to see those numbers once.
You mention non gm maf giving false readings or not being properly scaled. Who makes the 2007-2014 gm truck suv maf sensors for gm. I know if you order certain gm parts they show up with denso on ac compressors and ntk on 02 sensors which can be bought for substantially less money.
What was the ROOT CAUSE though????
So what caused it to register that high of reading?
Glad I found this video! I’m having similar issue with my 08 Avalanche. It was originally Flex, I swapped for a regular gas LS motor last year & was running fine. This last month it’s been running really rich with a p0300 code. & suggestions on where to start? I’m in the process of changing spark plugs now. Thanks n advance (:
I had a throttle body relearn done to fix the constant problem after cleaning it. I think I may have made a mistake I did a fuel composition reset using X431 on my 2011 5.3 flex fuel suburban , currently have e85 in my tank. Now I have 2 code errors p0171-00 and p0174-00 fuel trim lean system lean bank 1 and 2. Did I do something wrong? I would appreciate any help what to do and proceed. Thank you
Appreciate that!!! Learned me something new
Hey you had mentioned most cheaper code readers can do this function. Is there any you can recommend. I just purchased one from Amazon and I made the assumption it could do this reset due to price. But it is not able to reset content. Mines at 62% and both long terms are pegged at -30
Alcohol is not your friend. My 2013 fifteen hunnert has the 4.8 and the same flex fuel sticker as your subject vehicle. Mine is also fahr ingin red but doesn't have a siren. More good info here stored in my memory banks should such a situation arise. I don't see any E gas available around where I live, but it was omnipresent during a recent trip into the heartland.
What happened the next time that customer filled up? I'm afraid that the next fill up it shot back up to 60-80% again.
2007 suburban.. it creeps up to 80% about every 4 months or so… then I've reset it… was up ? Bad o2 maybe?
My ltft is at 30 after I rest my achole
Eric: "That's why alcohol is dangerous"
Me on my 4th rum and coke while watching SMA: "Wooooooooow…. I feel attacked right now."
REV up the part canon
Hey Eric, ONCE, I thought I was wrong, but, I was mistaken
What is a good scan tool that I can use to do this without breaking the bank?
ethanol needs to be removed from all gas.
What type of scanner can I buy to do this reset myself and check my fuel alcohol levels
Great videos! What's your take on Catch Cans, do you like them for Chevys?
ERIC PO451 tank pressure sensor after market fuel pump GMC Sierra 1500 flex fuel that code keeps coming up after install 29 percent alcohol level have seen the evap solenoid code also PO446 which is not coming up now just the PO451 is this a bad tank pressure sensor on a crappy aftermarket fuel pump this is the second one installed under warranty if 5 volt reference is there what could it be causing this code other than a tank pressure sensor that is not working well on this fine GM product 🙄