Just filled up gas tank. Gas gauge is moving from full to empty. Orange fuel tank shaped gas light is blinking. When car is stopped at light the gauge starts to go down towards empty. When underway gauge moves back up and blinking gas light goes out. Gas cap is on tightly and there is no gasoline smell. Any idea what is going on?

SOURCE: gas gauge reads full when underway. However, when

Most likely it a bad fuel level sensor on you fuel pump. You will have to replace the fuel pump as that is the only way to replace the sensor for you fuel gauge. The sensor is built into the fuel pump. The contacts on the sensor become corroded over time and cause the sensor to malfunction causing your fuel gauge to read full all the time. I have a 2001 Montana extended version that had the same problem. In order to know when I needed to fill the tank, I would completely fill it each time I put fuel in and reset my trip odometer. I would go 400 miles on the tank before I would refuel until we were able to replace the fuel pump.

SOURCE: gas gauge reading empty even when tank is full

Usually if the gas gage does not work yes it is true it may be the sensor if it is electronicly controlled. the sncor will more than likley be in the tank. here is how to remove your gas tank.

1. Before servicing the vehicle, refer to the precautions section.
   
2. Relieve fuel system pressure.
   
3. Drain the fuel tank.
   
4. Remove or disconnect the following:
   
   • Negative battery cable
     
   • Fuel filler and vent hoses
     
   • Fuel tank skid plate
     
   • Fuel tank wiring connectors
     
   • Fuel supply and return lines
     
   • Fuel tank
     
   • Fuel pump assembly
     Fuel pump assembly mounting
     

1. Install or connect the following:
   
   • Fuel pump assembly
     
   • Fuel tank. Tighten the bolts to 27 ft. lbs. (36 Nm).
     
   • Fuel supply and return lines
     
   • Fuel tank wiring connectors
     
   • Fuel tank skid plate
     
   • Fuel filler and vent hoses
     
   • Negative battery cable
     
2. Start the engine and check for leaks.
   

SOURCE: 2001 Rodeo giving false fuel gauge readings

my 2000 rodeo had same problem . i finally found a bad electrical connection in plug inside the lower left kick panel. the plug connection was not staying fully inserted into the other half of the connector the wire and crimped connector would completley come out of the molded plastic plug that had multiple wires inserted in it . i had to route around to the mating wire on the other half of the connector and connected with a sta-kon connector . there are many connections in this circuit you may have to check all of them. the fuel pump / sending unit did not fix my problem so i went checking connections .this was a fault from who ever made the wiring harness
GOOD LUCK AND MAY GOD BLESS YOU !!!!