If you have plenty of fuel in the tank, then there could be a problem in the fuel system. First, make sure the fuel cap is properly installed and in good condition. If in doubt, have it checked or replace it. Another possibility is a leak in the fuel Evaporative Emissions (EVAP) control system. This system deals with fuel vapors coming from the fuel tank. The vapors are routed to the intake system. If there's a leak in this system, the fuel light will flash.