P0455 on a 2018 Ford F 250 Regular Cab

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 Regular Cab

Ranked from 382 NHTSA owner complaints filed for this vehicle.

Sort by:

1
Stuck EVAP purge valve or fuel-tank vent/check valve
Medium severity
One owner's mechanic traced sputtering and long-crank symptoms to a stuck EVAP purge/check valve letting fuel-line and vapor pressure bleed off overnight.
Reported in 1 NHTSA complaint
Parts:EVAP purge valve fuel tank vent valve
2
Charcoal canister crack
Medium severity
The same complaint recommends replacing the EVAP canister as part of the fix, consistent with a larger canister-related leak path.
Reported in 1 NHTSA complaint
Parts:EVAP canister
3
Loose, missing, or damaged gas cap
Low severity
A cap that isn't sealing at all is the most common source of a large EVAP leak code.
Common cause
Parts:fuel filler cap
4
Disconnected or split EVAP hose/line
Medium severity
A fully detached or split vapor line produces a large, easily-detected leak.
Common cause
5
Rusted or corroded fuel filler neck
Low severity
Significant corrosion can open a large leak path around the filler neck.
Common cause
6
EVAP vent valve solenoid stuck open
Medium severity
A vent valve stuck fully open prevents the system from sealing at all during the EVAP monitor.
Common cause
Parts:EVAP vent valve

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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