P0455 on a Ford: Causes, Fixes & Repair Cost

🟢 Low severity · drivable

Safe to drive — this is an emissions leak, not an engine problem, but fix it before your next emissions test.

What P0455 means on a Ford

On a Ford, P0455 means the engine computer has detected a large leak in the evaporative emission (EVAP) system, so fuel vapors are escaping. Many newer Fords use a capless fuel filler, which can't be left loose but can still fail to seal, while older Fords with screw caps can trigger the code from a loose cap.

Is P0455 common on Fords?

P0455 is a common code on Fords like the F-150, Escape, Focus, and Explorer. With capless fuel fillers, the seal around the filler neck is the thing to inspect; on older models, the gas cap is still the first suspect.

Commonly reported on: F-150, Escape, Focus, Explorer.

Symptoms

Check engine light is on
Possible fuel smell
No change in performance
Emissions test failure

Common causes

most common: Loose or damaged gas cap on screw-cap models
common: Capless fuel filler seal not closing properly
common: Disconnected or cracked EVAP hose
less common: Faulty EVAP purge or vent valve

How to fix it

Fix	DIY?	Typical cost
Tighten or replace the gas cap on screw-cap models	Yes	$10–30
Inspect and clean the capless fuel filler seal	Yes	$0–20
Have a smoke test performed to find the exact leak	Mechanic	$50–150
Replace the capless filler assembly if it won't seal	Mechanic	$100–250