P0455 on a 2015 Ford Focus

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 2015 Ford Focus

Ranked from 1,022 NHTSA owner complaints filed for this vehicle.

Sort by:

1
Canister purge valve failure (stuck open/leaking)
High severity
Dominant pattern in this batch: repeated stalling (often right after refueling), rough/surging idle, and P1450/P144A-type EVAP codes traced to a failed canister purge valve; this is the subject of Ford recall 18S32/NHTSA 18V735 on Focus models, and many owners report the same failure recurring even after the recall repair.
Reported in 16 NHTSA complaints
Parts:canister purge valve
2
Warped/deformed plastic EVAP fuel tank
Medium severity
Several complaints describe a heat-warped or deformed plastic fuel tank (inspected as part of the same purge-valve recall) disrupting EVAP system sealing and vapor flow.
Reported in 1 NHTSA complaint
Parts:fuel tank
3
Loose, cracked, or missing gas cap
Low severity
A gas cap that won't seal (worn gasket, cross-threaded, or left off) is the single most common trigger for a small/large EVAP leak code; check cap first.
Common cause
Parts:gas cap
4
Cracked or brittle EVAP vapor/vent lines and hoses
Medium severity
Age- and heat-cracked rubber or plastic EVAP lines under the vehicle or in the engine bay allow vapor to escape; smoke-test to pinpoint.
Common cause
5
Canister vent valve (CVS) failure
Medium severity
A vent valve that won't seat allows the EVAP system to bleed to atmosphere, preventing the system from holding vacuum/pressure during self-test.
Common cause
Parts:canister vent valve
6
Charcoal canister crack or saturation
Medium severity
A cracked canister body or one saturated from repeated overfilling can leak vapor or restrict purge flow.
Common cause
Parts:charcoal canister
7
Corroded or rusted fuel filler neck
Low severity
Rust-through on the filler neck (common in road-salt regions) creates a leak path the EVAP monitor detects as a large leak.
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