https://stream.echo6.co/videos/watch/18e44e6f-de01-4f4d-8ef7-5ef620acfe8b 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) If an SMA Video has helped you out please consider giving using "Patreon" to help support us. The videos take real time to create and pull us away from real work that pays our bills. CLICK HERE: https://www.patreon.com/southmainauto THANKS A MILLION!! --Eric O. WANT AN "SMA" STICKER OF YOUR OWN!?! Simply send and E-mail to SMAstickers@outlook.com including: your shipping address and e-mail address in the text, I in turn will send you a paypal invoice for $5 each USA or $6 each international. Let me know how many you want and as soon as the paypal invoice is paid I will ship them out ASAP! Thanks for your support of our channel!! --Eric & Vanessa O. Feel like sending some swag to SMA because you love the videos but don't know where to send it? Just ship it here: South Main Auto Repair 47 S. Main St PO Box 471 Avoca, NY 14809 Disclaimer: Due to factors beyond the control of South Main Auto Repair, it cannot guarantee against unauthorized modifications of this information, or improper use of this information. South Main Auto Repair assumes no liability for property damage or injury incurred as a result of any of the information contained in this video. South Main Auto Repair recommends safe practices when working with power tools, automotive lifts, lifting tools, jack stands, electrical equipment, blunt instruments, chemicals, lubricants, or any other tools or equipment seen or implied in this video. Due to factors beyond the control of South Main Auto Repair, no information contained in this video shall create any express or implied warranty or guarantee of any particular result. Any injury, damage or loss that may result from improper use of these tools, equipment, or the information contained in this video is the sole responsibility of the user and not South Main Auto Repair. Tue, 12 May 2026 13:27:28 GMT https://validator.w3.org/feed/docs/rss2.html PeerTube - https://stream.echo6.co https://stream.echo6.co/client/assets/images/icons/icon-512x512.png https://stream.echo6.co/videos/watch/18e44e6f-de01-4f4d-8ef7-5ef620acfe8b All rights reserved, unless otherwise specified in the terms specified at https://stream.echo6.co/about and potential licenses granted by each content's rightholder.