P0455 on a 2020 Ford Explorer

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 2020 Ford Explorer

Ranked from 1,171 NHTSA owner complaints filed for this vehicle.

Sort by:

1
Purge valve malfunction (stuck open/closed)
Medium severity
Directly reported multiple times, including a documented P0496 evaporative purge-valve fault and a purge valve that wouldn't let the vehicle start after refueling — a failed purge valve breaks the EVAP system's ability to seal for leak testing.
Reported in 3 NHTSA complaints
Parts:purge valve
2
Fuel filler neck / capless fuel-fill valve malfunction
Medium severity
Owners report the fuel nozzle repeatedly clicking off and fuel spitting back during fill-ups, a classic sign of a sticking capless filler-neck valve that also compromises the EVAP seal.
Reported in 2 NHTSA complaints
Parts:fuel filler neck assembly
3
Loose or damaged gas cap/filler seal
Low severity
An incompletely seated or worn filler seal is the single most common real-world trigger for small EVAP leak codes.
Common cause
4
Cracked or aged EVAP vent/purge lines
Low severity
Heat-cycled rubber or plastic EVAP lines crack over time, opening a leak path in the system.
Common cause
5
Charcoal canister crack
Medium severity
Corrosion or impact damage to the canister housing creates a direct, often large, EVAP leak.
Common cause
Parts:charcoal canister
6
Rusted or corroded filler neck
Medium severity
Road-salt corrosion can perforate the filler neck over time, most common in northern climates.
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