The P0455 is a common code since it will set if the gas cap is loose or missing. Start by tightening the gas cap and clearing the code. In most cases, the code can be clear by disconnecting the car battery for about 30 minutes.
The PCM monitors the complete EVAP control system for no purge flow, the presence of a large fuel vapor leak, or multiple small fuel vapor leaks. The system failure occurs when no purge flow (attributed to fuel vapor blockages or restrictions), a large fuel vapor leak, or multiple fuel vapor leaks are detected by the EVAP running loss monitor test with the engine running (but not at idle).
There is a factory service bulletin for the 2001 Ford F-150:
2001 Ford F-150 Factory Service Bulletin OBDII Code P0455
Check the 'Possible Causes' listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.
The cost to diagnose the P0455 2001 Ford F150 code is 1.0 hour of labor. The diagnosis time and labor rates at auto repair shops vary depending on the location, make and model of the vehicle, and even the engine type. Most auto repair shops charge between $75 and $150 per hour.
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.
The Diagnostic Trouble Code (DTC) will set when the EVAP control system has a very large leak such as the fuel filler cap fell off, the EVAP control system does not operate properly.
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