P0455 on a 2017 Ford Escape

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 Escape

Ranked from 2,628 NHTSA owner complaints filed for this vehicle.

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1
Stuck-open EVAP purge valve/solenoid
Medium severity
Documented on this vehicle: a purge valve confirmed stuck open, and another case with the purge solenoid replaced twice for a P1450 code — a valve stuck open leaves the system essentially unsealed, large enough to read as a large leak.
Reported in 2 NHTSA complaints
Parts:EVAP purge valve EVAP purge solenoid
2
Disconnected, split, or failed EVAP fuel vapor line/assembly
Medium severity
One owner had the dealer replace the EVAP fuel vapor assembly after a code diagnosis, consistent with a large vapor-path breach.
Reported in 1 NHTSA complaint
Parts:EVAP fuel vapor line
3
Loose or missing fuel filler cap
Low severity
The most common large-leak trigger; a cap that isn't tightened/seated fails the monitor's coarse leak test almost immediately. Most fuel/propulsion-tagged complaints on this vehicle are the unrelated EcoBoost coolant-intrusion issue and were excluded here as not code-consistent.
Common cause
Parts:fuel filler cap
4
EVAP vent valve (CVV) stuck open
Low severity
A vent valve stuck fully open holds the system at atmospheric pressure, which the monitor reads as a large leak.
Common cause
Parts:EVAP vent valve
5
Cracked charcoal canister housing
Low severity
A larger canister crack can be big enough to register as a large rather than small leak.
Common cause
Parts:EVAP charcoal canister
6
Rusted-through fuel filler neck
Low severity
Advanced corrosion can perforate the filler neck outright, producing a leak large enough to set P0455.
Common cause
Parts:fuel filler neck

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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