P0455 on a 2024 Mazda Cx 90 Phev
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 2024 Mazda Cx 90 Phev
Ranked from 407 NHTSA owner complaints filed for this vehicle.
- 1
EVAP/fuel-vapor system malfunction with raw fuel-vapor odor (reported fuel tank pressurization failures on this model)
High severityMultiple owners describe a fuel tank pressurization system failure and a persistent raw gasoline vapor smell, consistent with a purge/vent circuit that won't seal at all.
Reported in 2 NHTSA complaints - 2
Fuel filler door/gas cap access fault
Low severityA gas door reported stuck closed can prevent the cap from being seated at all.
Reported in 1 NHTSA complaint - 3
Loose or missing gas cap
Low severityThe single most common cause of a large-leak code.
Common causeParts:gas cap - 4
Large EVAP hose split or disconnected fitting
Medium severityA fully detached or split line is the typical mechanical cause of a large-leak code.
Common cause - 5
EVAP canister vent valve stuck open
Medium severityA vent valve stuck open prevents the system from ever pressurizing.
Common causeParts:canister vent valve - 6
Charcoal canister crack
Medium severityA cracked canister housing is a common large-leak path.
Common causeParts:charcoal canister - 7
Rusted or damaged fuel filler neck
Medium severityCorrosion or a torn filler neck seal lets the tank vent to atmosphere.
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.