My 1999 Isuzu Rodeos gas gauge shows empty with gas light on all the time even when full . has worked once in last week but very slow coming up

sounds like you may have a bad fuel level sender problem. as for the check engine light coming on and storing a fault code that is a separate issue.

If the trouble with the gauge started after you worked on it then you likely damaged or created a restriction to the movement of the sending unit. You will have to remove the tank and double-check your work.

The float in the tank might be leaking and since it has gas in it, its showing empty.

Open the oil filler cap, insert a funnel, pour oil into funnel until qt. bottle is empty, remove funnel and replace filler cap.

fuel level sensor is part of the fule pump assembly. code is telling you sensor is malfuctioning. do gauges work? if yes i would leave problem alone till you need a fuel pump

Fuel level sending units are known to go bad on these.

sounds like the float is either got a hole in it and is full of fuel, or the whole float assembly is seized in the empty position.
was the car left for 5 weeks empty of fuel?

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
     

To install:

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.
   

The problem usually lies in the wiring harness.

Traction Light has a traction system sensor going bad.
Blinker rapid flash- brakes applied, Need to replace dual function tail lamp bulb(brake turn
bulb)
Reverse light need shifter adjustment.
Gas gauge The sending unit in your tank is going bad replace it.