The P0455 it’s a very common code, because the code is set if the gas cap is loose or missing. Start by tighten the gas cap and clearing the code. In most cases the code can be clear by disconnecting the car battery for about 30 minutes.
There is a factory service bulletin for the following vehicles:
1997-2000 Ford Contour 1997-2002 Ford Escort 1997-2003 Ford Crown Victoria 1997-2003 Ford Mustang 1997-2003 Ford Taurus 1998-2003 Ford Escort ZX2 2000-2003 Ford Focus 2002-2003 Ford Thunderbird 1997 Ford F-250 HD 1997-1999 Ford F-250 LD 1997-2003 Ford E Series 1997-2003 Ford Expedition 1997-2003 Ford Explorer 1997-2003 Ford F-150 1997-2003 Ford Ranger 1997-2003 Ford Windstar 1999-2003 Ford F Super Duty 2000-2003 Ford Excursion 2001-2003 Ford Escape 2001-2003 Ford Explorer Sport Trac 2001-2003 Ford Explorer Sport Ford Factory Service Bulletin OBDII Code P0455
EVAP control system has a very large leak such as fuel filler cap fell off, EVAP control system does not operate properly.
Engine Light ON (or Service Engine Soon Warning Light)
Possible a noticeable fuel odor caused by the release of fuel vapors
P0455 Ford Description
Vehicles that meet enhanced evaporative requirements utilize a vacuum-based evaporative system integrity check. The evap system integrity check uses a Fuel Tank Pressure Transducer (FTPT), a Canister Vent Solenoid (CVS) and Fuel Level Input (FLI) along with the Vapor Management Valve (VMV) or Electric Vapor Management Valve (EVMV) to find 0.040” diameter or larger evap system leaks. Federal vehicles can utilize a 0.040" leak check rather than the 0.020" leak check required for California vehicles.