P0455 on a 2018 Kia Soul

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 2018 Kia Soul

Ranked from 211 NHTSA owner complaints filed for this vehicle.

Sort by:

1
EVAP purge or vent valve malfunction (electrical/solenoid fault rather than a physical leak)
Medium severity
One owner's mechanic diagnosed the code but a smoke test found no leak, which for a large-leak code points toward a valve that's stuck open/not sealing or a wiring/connector fault rather than a torn hose.
Reported in 1 NHTSA complaint
Parts:purge valve vent valve
2
Fuel vapor leak (owner-reported gasoline odor while driving)
Medium severity
A reported gasoline smell while driving is consistent with a sizeable evaporative leak; a smoke test will localize it quickly.
Reported in 1 NHTSA complaint
3
Missing, loose, or badly worn gas cap
Low severity
A cap that isn't sealing at all (or is missing) is the single most common cause of a large-leak EVAP code.
Common cause
Parts:gas cap
4
Disconnected or split EVAP hose
Medium severity
A hose that has popped off a fitting or split open creates a leak large enough to fail the system's large-leak threshold outright.
Common cause
Parts:EVAP hose
5
Charcoal canister crack or damage
Medium severity
Physical damage to the canister (impact, corrosion) opens a large enough path to atmosphere to trip this code.
Common cause
Parts:charcoal canister
6
Rusted-through filler neck
Medium severity
Significant corrosion at the filler neck can open a large enough gap to fail the leak test.
Common cause

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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