P1450. Tough one to figure out. Could be Canister Vent Solenoid, Vapor Management Valve, Fuel Tank Pressure Sensor, charcoal canister, evap hoses, or wiring. Or a combo of those things. If you fill gas and it stops before tank being full it could be blocked hoses or defective Canister Vent Solenoid (above spare tire next on the charcoal canister). I replaced mine and it fills all the way now but still had the P1450 code. I replaced Vapor Management Valve (in engine compartment drivers side firewall). Only thing left on my list to clean, test, or replace was the FTP sensor. That was a pain to replace as it was on top of fuel tank next to fuel pump. Involved dropping tank and splicing new short fuel lines (5/8"? fuel hose with twist clamps and hose connectors) to connect to new sensor and connecting the harness. FTP sensor alone on ebay was $30 otherwise dealer part with all the hoses and connections for $350(?). Dealer wanted $1700 just to drop tank, throw parts at it, and investigate more. I dropped the tank and replaced FTP sensor with misc hose parts. That got rid of the P1450 code.
2005 Navigator