Fuel-Tank-Level-Sensor

The fuel tank level sensor tells the ECM about fuel level. This is not a simple fuel level sensor that actuates the dash fuel gauge. This sensor informs the ECM of fuel level so that is can run the EVAP monitor test. This test is done by pressurizing the fuel tank with air or vacuum and detecting a leak. This test will not run on an empty tank, hence the need for the fuel level sensor. See how it works here.