Older Ford F-150 models did not contains a specific dash light for a loose or faulty fuel cap. Previously, the "Check Engine" light would simply illuminate. In newer models, the term "Check Fuel Cap" or a symbol of a gas cap may appear below the speedometer. This is not cause for alarm--in most cases, the fuel cap is misaligned or improperly tightened. However, it's possible that it needs to be replaced. A replacement fuel cap generally costs between $10 and $15, certainly not a major expense.
Park your F-150 in a safe place and shut the engine off.
Open your F-150's fuel filler door and examine the fuel cap. If the "Check Fuel Cap" message appears on your dash, the fuel cap is either improperly attached (misaligned or not tight enough) or damaged.
Turn the fuel cap handle one-quarter turn counterclockwise to remove it. Reattach and align the fuel cap with the filler neck opening. Turn the fuel cap clockwise until it "snaps" twice.
Continue driving your truck normally. If the fuel cap was misaligned, off, or improperly attached, it may take a day or two for the light to go off.
Replace the fuel cap if the light does not go off. If your F-150 is under the original manufacturer's warranty, the cap will be covered. Replace the fuel cap with a factory replacement to ensure compatibility.
