What unit did you replace. The fuel gauge,sending unit in tank or the bcm(body control module) which controls the gauge. Try grounding the wire to the sending unit it should read a full tank of fuel. If it does the sending unit in the tank is bad or you may have a bad ground or missing ground strap to the fuel tank as this tank is plastic it needs the ground strap. If the gauge does not move then you need to check to see if the bcm has a good connection to the wire for the sending unit. Check the wire with an ohm meter. The fuel gauge can be tested and adjusted with a DRB III, which is a dealership scanning tool. If you don't have this tool and have not found a problem with the wiring to the sending unit or the ground circuit, I reccomend you take it in to a dealer to have it fixed. Goodluck Greasemonkey
If you can find a good repair shop with a cry or snap on scanner.
They have a dash gauge test function.
That will separate dash gauge from a fuel sending unit problem or as said ground the fuel tank sending unit wire and see if gauge moves.