P0455 on a 2017 Ford Fusion

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 2017 Ford Fusion

Ranked from 1,096 NHTSA owner complaints filed for this vehicle.

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1
Large EVAP vacuum/vent-path fault causing fuel-tank pressure imbalance
Medium severity
Recurring reports of honking/sucking noises from the fuel tank, hard restart after fueling, and stalling at fill-up point to a restricted or leaking vent path rather than a simple cap issue.
Reported in 4 NHTSA complaints
2
Canister purge valve (CPV) stuck open, causing a large, continuous EVAP leak
High severity
One owner had the purge valve replaced three times for the same failure mode, and another owner's mechanic diagnosed a stuck-open purge valve creating excess fuel-tank vacuum.
Reported in 3 NHTSA complaints
Parts:purge valve
3
Loose, cross-threaded, or worn fuel filler cap
Low severity
The single most common trigger for a small EVAP leak code; check that the cap clicks fully and the seal isn't cracked before condemning any other component.
Common cause
Parts:fuel cap
4
Cracked or damaged EVAP canister
Medium severity
A cracked canister housing lets vapor escape past the carbon bed; smoke-test the canister assembly to confirm.
Common cause
Parts:EVAP canister
5
Cracked or brittle EVAP lines
Medium severity
Heat- and age-cracked rubber EVAP lines under the vehicle are a frequent small-leak source; smoke-test the system to pinpoint.
Common cause
Parts:EVAP lines
6
Rusted or corroded fuel filler neck
Low severity
Rust-through of the filler neck creates a leak path that a smoke test will reveal; more common on high-mileage, road-salt-exposed vehicles.
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