P0455 on a 2021 Kia Seltos

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 Kia Seltos

Ranked from 346 NHTSA owner complaints filed for this vehicle.

Sort by:

1
Fuel system line/fitting leak
Medium severity
A complaint describes noticeable gas fumes resolved by replacing the fuel pump and its gaskets/fittings, consistent with a leak large enough to register.
Reported in 1 NHTSA complaint
Parts:fuel line fuel pump gasket
2
Faulty fuel tank pressure sensor
Low severity
A complaint reports the tank sensor failing to detect fuel correctly, which can register as a false large-leak result even with a sealed system.
Reported in 1 NHTSA complaint
Parts:fuel tank pressure sensor
3
Loose, missing, or improperly seated fuel filler cap
High severity
The classic large-leak cause; a cap left loose or cross-threaded produces a leak big enough to fail the large-leak EVAP test almost immediately.
Common cause
Parts:fuel cap
4
Disconnected, cracked, or pinched large EVAP hose/line
Medium severity
A fully cracked or knocked-loose EVAP line creates a large, continuous leak path.
Common cause
Parts:EVAP hose
5
Purge valve stuck open
Medium severity
A purge valve stuck open creates a large, unmetered path to atmosphere that the large-leak monitor readily detects.
Common cause
Parts:purge valve
6
Vent valve stuck open
Medium severity
A vent valve that won't close prevents the EVAP system from sealing at all, guaranteeing a large-leak result.
Common cause
Parts:vent valve
7
Charcoal canister crack
Low severity
A significantly cracked canister housing can open a large enough leak path to fail the large-leak test.
Common cause
Parts:charcoal canister

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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