Before doing tests on the unit that measures the fuel amount, verify how full the tank really is. Remove the fuel tank from the vehicle. Take the fuel pump/Fuel Level Sensor off from the fuel tank. To check resistance in the fuel level sensor, place the ohmmeter probes on the connector ends and browse the meter's 200-ohm scale. To check the sensor, measure its resistance once when the float arm is all the way down (empty fuel tank) and again when it's all the way up (full tank); the reading should keep changing consistently. As the fuel tank runs down, the resistance of the sensor should first be around 110 ohms, and should be close to 3 ohms when the tank is full. If readings show problems, you need to replace the sensor. Take the fuel pump/Fuel Level Sensor assembly out of the fuel tank, carefully guide the sensor through the opening without harming the bottom fuel level float, disconnect the electrical wires from the assembly, and unscrew the bracket side bolt to separate the sensor from its mount. Installation is the reverse of removal.