Why would check engine light on in ford explorer come on after fueling with ethanol?

The check engine light in a Ford Explorer may come on after fueling with ethanol due to a few reasons. Ethanol can cause a change in fuel composition, possibly affecting the vehicle's air-fuel mixture or triggering sensors like the oxygen sensor or fuel system monitors. Additionally, if the fuel cap wasn't securely tightened, it can lead to a vacuum leak, prompting the check engine light to activate. It's advisable to check for any diagnostic trouble codes to determine the exact cause.