P0455 on a 2017 Toyota Tacoma

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 Toyota Tacoma

Ranked from 237 NHTSA owner complaints filed for this vehicle.

Sort by:

1
Fuel filler door damaged/won't close, breaking the cap seal
Low severity
One owner reports the fuel filler door broke and would no longer close, leaving the cap area unsealed and producing a leak large enough to register as a gross EVAP leak.
Reported in 1 NHTSA complaint
Parts:fuel filler door gas cap
2
EVAP leak-detection pump / charcoal canister assembly beginning to fail
Medium severity
An owner reports the leak detection pump sub-assembly at the charcoal canister pumping loudly for extended periods, indicating the EVAP monitor is struggling to seal/test the system.
Reported in 1 NHTSA complaint
Parts:leak detection pump charcoal canister
3
Missing, loose, or improperly seated gas cap
Low severity
A cap that isn't fully sealed is the most common trigger for a large EVAP leak code.
Common cause
Parts:gas cap
4
Disconnected or split EVAP hose/line
Medium severity
A hose popped off a fitting or split open creates a large leak path the EVAP monitor detects quickly.
Common cause
5
Vent valve stuck open or failed
Medium severity
The canister vent valve must seal for the EVAP system to build test vacuum; a stuck-open valve reads as a gross leak.
Common cause
Parts:vent valve
6
Cracked charcoal canister
Medium severity
A cracked or corroded canister housing leaks fuel vapor directly to atmosphere.
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