P0455 on a 2018 Ford F 250 Supercab

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 250 Supercab

Ranked from 397 NHTSA owner complaints filed for this vehicle.

Sort by:

1
Stuck-open EVAP purge valve
Medium severity
A detailed owner complaint describes a faulty EVAP purge valve sticking, which can produce a large, continuous vapor leak path.
Reported in 1 NHTSA complaint
Parts:EVAP purge valve
2
Failed EVAP canister/vent components from dust ingress
Medium severity
The same complaint describes dust entering the EVAP vent line and reaching the canister and fuel-sending unit, degrading seals enough to produce a larger leak.
Reported in 1 NHTSA complaint
Parts:EVAP canister
3
Aftermarket emissions system deletion/modification
Low severity
One owner discovered the truck's emissions equipment had been deleted before purchase; removed or bypassed EVAP hardware is a direct cause of large-leak EVAP codes.
Reported in 1 NHTSA complaint
4
Loose, damaged, or missing fuel filler cap
Low severity
A cap that fails to seal is the most common cause of a large EVAP leak and is the first thing to check.
Common cause
Parts:fuel cap
5
Cracked, disconnected, or pinched EVAP hose/line
Medium severity
A fully disconnected or split EVAP line creates a large, unmistakable vapor leak that will set P0455 quickly.
Common cause
Parts:EVAP hose
6
Rusted or damaged fuel filler neck
Low severity
A corroded filler neck can develop a hole or a poor seal against the cap flange, producing a large, continuous leak.
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