Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
i have a 2011 gmc yukon denali that takes flex fuel and regular gas. someone working on my truck reset my codes when it had flex fuel in it. it is only supposed to be done when it has regular fuel, now it won;t run with 85. what can i do?
I have never heard of clearing codes on a flex fuel vehicle causing that kind of problem. I wouldn't be so quick to blame the last guy who worked on it....
If the flex fuel composition is incorrect and causing driveability issues, it can be reset with a scan tool
Someone reset the codes? Or reset the Fuel Alcohol Content %? I agree with Noah, clearing fault codes alone will not reset the Fuel Alcohol Content %. The content % only gets reset when the ECM is replaced or someone uses the Fuel Composition Reset function.
If the Fuel Composition Reset function got used and there really is E85 in the tank, then you're a bit stuck. An alcohol content relearn is only triggered when the ECM sees a sufficient amount of increase in fuel level (a refueling event). If there's enough room in the tank, you can top it off and see if you can trigger a relearn. Otherwise, you'll need to drain the tank and refill with E15. From service info:
When an engine control module (ECM) is replaced or when the Fuel Composition Reset has been performed with a scan tool, the fuel system will need to contain ASTM gasoline with 10 percent or less ethanol content.
If the fuel in the fuel system needs to be drained and replaced with ASTM gasoline, the engine will need to run at operating temperature and consume at least 1 liter (0.3 gallon) of fuel to flush out any remaining non-ASTM fuel. The fuel at the fuel rail will need to be rechecked to verify that 10 percent or less ethanol is now at the fuel rail. At this time the Fuel Composition Reset can be performed and will default to 3 percent.
Resetting the system restores the vehicle to factory fill conditions and 10 percent or less ASTM gasoline must be present for future calculations. Resetting the system does not cause a relearn event to occur. The system will now be able to recognize the correct ethanol content in the future. Either ASTM gasoline or ASTM E85 fuel can then be used.
Topic Author
