P0455 on a 2017 Ford F 150 Crew 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 2017 Ford F 150 Crew Cab

Ranked from 1,066 NHTSA owner complaints filed for this vehicle.

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1
Capless ('Easy Fuel') filler seal or inlet check-valve leak
High severity
Two owners report fuel vapor escaping at the capless filler (smell of gas, spray on refuel) with the vehicle under 5,000-15,000 miles — a sizable, well-documented leak path on this filler design.
Reported in 2 NHTSA complaints
Parts:fuel filler seal capless filler check valve
2
Cracked or leaking fuel line
Medium severity
Two complaints describe a pressurized fuel line leaking at a fitting near the tank (one owner reporting it as the third such repair), a large and obvious leak.
Reported in 2 NHTSA complaints
Parts:fuel line
3
Fuel tank pressure/venting fault during towing (TSB-documented stall)
Medium severity
A Ford TSB covers intermittent stalls on 2.7L-equipped trucks tied to fuel tank venting/pressure while towing; two complaints match this exact TSB.
Reported in 2 NHTSA complaints
4
Purge valve stuck open
Medium severity
A purge solenoid stuck open holds the EVAP system open to intake vacuum, which the monitor reads as a large leak.
Reported in 1 NHTSA complaint
Parts:purge valve
5
Vent valve stuck open or failed
Medium severity
A vent valve that won't close prevents the EVAP system from sealing at all, the classic large-leak failure mode.
Common cause
Parts:vent valve
6
Rusted or corroded filler neck / fuel tank
Low severity
Corrosion or physical damage to the tank/filler neck creates an unmistakable large 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