P0455 on a 2018 Ford F 150 Super Crew

P0455 means the EVAP system failed a leak check badly enough that the computer sees a large leak or no pressure/vacuum change.

Not your vehicle? See general P0455 info.

Most common causes on the 2018 Ford F 150 Super Crew

Ranked from 1,835 NHTSA owner complaints filed for this vehicle.

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1
Capless fuel filler door/seal failure
Medium severity
The same documented hinge-spring/swivel-pin wear that lets the capless filler door pop open can, when severe, produce a large rather than small leak result.
Reported in 1 NHTSA complaint
Parts:fuel filler door seal
2
Cracked or disconnected fuel vapor line
Medium severity
A persistent gasoline smell in the cabin after driving is consistent with a sizable EVAP/fuel vapor line leak; smoke-test to pinpoint.
Reported in 1 NHTSA complaint
Parts:EVAP hose
3
Purge valve stuck open
Medium severity
A valve stuck fully open removes the system's ability to seal for the leak test, producing a large-leak result.
Common cause
Parts:purge valve
4
Vent valve/solenoid failure
Medium severity
A vent valve that won't close keeps the tank open to atmosphere, guaranteeing a large-leak fail.
Common cause
Parts:EVAP vent valve
5
Cracked charcoal canister
Medium severity
A significant crack or split seam in the canister produces a large-leak result.
Common cause
Parts:charcoal canister
6
Corroded fuel tank or filler neck
Medium severity
Rust-through on the tank or filler neck creates an obvious large leak path; check underbody for corrosion and fuel odor.
Common cause

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These causes are aggregated from NHTSA owner complaints and general repair knowledge — this is not a diagnosis. P0455 on your car still needs shop confirmation before any repair.

Common symptoms

Check engine light
Fuel smell
Usually no performance issue
Failed emissions readiness

What to check before replacing parts

Check the gas cap first

Look for: A loose, missing, or cross-threaded cap is by far the most common cause of a large EVAP leak code — if it doesn't click to full tightness or the seal is cracked, that's very likely the whole fault.

Inspect visible EVAP hoses

Look for: A large leak is often obvious: a hose disconnected at a fitting, split open, or chewed through (rodent damage is common) rather than a hairline crack.

Command the purge and vent valves with a scan tool

Look for: A valve that doesn't respond at all when commanded open/closed, or stays open when it should seal, prevents the system from holding pressure/vacuum and reads as a large leak.

Smoke-test the system

Look for: With a large leak, expect an obvious plume of smoke or a clearly audible hiss at the fault location — it should be easy to spot compared to a small-leak diagnosis.

Inspect the canister and filler neck

Look for: A cracked charcoal canister housing or a corroded/rusted-through filler neck (common on older vehicles) can leak enough to prevent the system from ever holding vacuum.

Rather have a pro handle it? Find a vetted local mechanic.

Matching symptoms

Check Engine Light