P0455 on a 2021 Ford Bronco Sport

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 2021 Ford Bronco Sport

Ranked from 665 NHTSA owner complaints filed for this vehicle.

Sort by:

1
Fuel odor / vapor escaping near cracked fuel injectors (recall 25V467)
High severity
Several owners report a persistent fuel odor alongside the open injector-cracking recall, consistent with raw fuel vapor escaping near the engine rather than being properly contained.
Reported in 17 NHTSA complaints
Parts:fuel injector
2
Purge valve stuck open
Medium severity
The same documented Bronco Sport purge-valve failures (stalling after fueling, confirmed bad valve, abnormal EVAP vapor-pressure/O2 readings) can fail fully open, giving a large continuous vapor leak rather than a small one.
Reported in 4 NHTSA complaints
Parts:purge valve
3
Charcoal canister crack or saturation
Medium severity
One vehicle's canister was found completely saturated with liquid fuel — enough to represent a large, unmetered vapor path.
Reported in 1 NHTSA complaint
Parts:charcoal canister
4
Loose, missing, or damaged gas cap
Low severity
The classic P0455 large-leak trigger — a cap left off or with a torn seal fails the very next EVAP monitor.
Common cause
Parts:fuel cap
5
Cracked or split EVAP hose/line
Medium severity
A fully split vapor line produces the larger leak rate that trips P0455 rather than P0442.
Common cause
6
Rusted or cracked filler neck
Medium severity
A corroded or physically damaged filler neck opens a large vapor path that the EVAP monitor flags immediately.
Common cause
Parts:fuel filler neck

Part links go to Amazon search results for this vehicle. As an Amazon Associate, WrenchConnect earns from qualifying purchases — always confirm fitment for your exact trim and engine before ordering.

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