P0455 on a 2018 Ford Explorer

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 Ford Explorer

Ranked from 713 NHTSA owner complaints filed for this vehicle.

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1
Fuel tank / EVAP system leak (recall-related fuel vapor intrusion)
High severity
Multiple owners describe a strong, persistent raw-fuel odor filling the cabin, with one explicitly tying it to Safety Recall 18S35 (fuel system EVAP leak) — a large enough leak to produce a noticeable cabin odor is consistent with a large-leak P0455 rather than a marginal P0442.
Reported in 7 NHTSA complaints
Parts:fuel tank EVAP hose/line fuel filler neck
2
Purge or vent valve stuck open
Medium severity
One owner had the purge valve replaced immediately before a throttle-body fault, confirming purge-side hardware issues on this vehicle that can also manifest as a large EVAP leak.
Reported in 1 NHTSA complaint
Parts:purge valve vent valve
3
Loose, missing, or unlatched gas cap
Low severity
The single most common cause of a large-leak EVAP code; a cap left loose or not clicked closed produces a big enough leak to trip P0455 almost immediately.
Common cause
Parts:gas cap
4
Cracked EVAP canister or large split in an EVAP hose
Medium severity
A larger crack or a fully split hose produces enough vapor leakage to fail the large-leak EVAP test.
Common cause
Parts:EVAP canister EVAP hose
5
Rusted-through fuel filler neck
Medium severity
Significant corrosion can perforate the filler neck enough to register as a large leak.
Common cause
Parts:fuel filler neck
6
Fuel tank pressure (FTP) sensor fault
Medium severity
A drifted or failed FTP sensor can falsely report a large pressure/vacuum change during the EVAP monitor test even when the system is physically sealed.
Common cause
Parts:fuel tank pressure sensor

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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