Because your question is in the ford section it will need to be moved to Nissan, I am also a Nissan expert and I can help you. Your 2005 X-Terra has a TSB that deals with the bad sending unit and the check engine light on.
October 4, 2007
2005-2008 FRONTIER/XTERRA/PATHFINDER; FUEL GAUGE ISSUES &/OR DTC P0461/2/3
The Parts Information section of this bulletin has been amended. No other changes have been made.
APPLIED VEHICLES:2005-2008 Frontier (D40)
2005-2008 Xterra (N50)
2005-2008 Pathfinder (R51)
D40 Vehicles built before 1N6 (*) D (****) 8C 405797
N50 Vehicles built before 5N1AN (*) 8 (**) 8C 504273
R51 Vehicles built before 5N1AR (*) 8 (**) 8C 630614
All Vehicles built before 19-Sept-2007
IF YOU CONFIRM:
The fuel gauge is erratic, inaccurate, or inoperative.
The MIL is "ON" with DTC P0461, P0462, or P0463 stored in Self-Diagnosis.
Replace the fuel level sending unit with the one from the Parts Information section of this bulletin. Refer to section FUEL LEVEL SENSOR UNIT, FUEL FILTER AND FUEL PUMP ASSEMBLY Disassembly and Assembly in the FL chapter of the appropriate ESM for details on the procedure, if needed.
NOTE: Do not replace the entire fuel pump assembly for this incident, if it should occur.