P0455 on a 2017 Kia Sportage

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 Kia Sportage

Ranked from 397 NHTSA owner complaints filed for this vehicle.

Sort by:

1
Missing, loose, or badly worn gas cap
Low severity
A gas cap that won't seal at all produces a large EVAP leak; this owner's cap needed repeated replacement and the tank could be heard gurgling, consistent with a large unsealed leak path.
Reported in 1 NHTSA complaint
Parts:gas cap
2
Rusted-through or badly deteriorated fuel filler neck
Medium severity
The same complaint describes ongoing rust and grime at the filler neck throat, a large enough opening to fail the EVAP monitor's large-leak threshold.
Reported in 1 NHTSA complaint
Parts:fuel filler neck
3
Rodent-damaged fuel/EVAP line causing a large leak
High severity
A chewed plastic fuel line producing a strong fuel odor is a large-opening leak source consistent with P0455's higher flow threshold.
Reported in 1 NHTSA complaint
Parts:fuel line
4
Purge valve stuck open
Medium severity
A purge valve stuck fully open lets in a large, continuous flow of outside air, easily exceeding the large-leak threshold.
Common cause
Parts:purge valve
5
Vent valve/canister vent solenoid stuck open
Medium severity
A vent solenoid that won't close prevents the EVAP system from ever sealing, which the monitor reads as a large leak.
Common cause
Parts:vent valve
6
Disconnected or badly cracked EVAP line
Medium severity
A hose that has popped off a fitting or split lengthwise creates a large, unrestricted leak path.
Common cause
7
Cracked charcoal canister housing
Low severity
A significant crack in the canister body is large enough to fail the large-leak EVAP 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