Fuel Hoses Lines/piping And Fittings problems of the 1998 Ford Expedition

Consumer noticed that engine check light engine light came on three weeks after she purchased the vechicle. She took vehicle back to the dealership, and the mechanic told her tha it was her gas cap. They replaced it, and she was still having problems. Also, they replaced a hose running though the fuel tank. But consumer was still having problems. Mechanic told her that fuel tank had a manufacturer's defect, and they would replace the part when it arrived. Consumer is driving a rental car.