P0455 on a 2017 Audi Q7

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 Audi Q7

Ranked from 316 NHTSA owner complaints filed for this vehicle.

Sort by:

1
Fuel rail / high-pressure fuel line leak (Audi recall 19V035)
High severity
Multiple owners report a strong gasoline odor traced to a leaking fuel rail or high-pressure pump fitting on the 3.0T engine, covered under NHTSA campaign 19V035; a raw fuel leak of this size is easily large enough to fail the EVAP leak monitor.
Reported in 6 NHTSA complaints
Parts:fuel rail fuel injector supply line high-pressure fuel pump
2
Fuel filler neck / vent flap defect
Medium severity
A broken or stuck filler-neck flap breaks the vapor seal at the fill point, documented via NHTSA bulletin/TSB on this generation, with fuel visibly splashing back during refueling in some cases.
Reported in 2 NHTSA complaints
Parts:fuel filler neck fuel tank vent valve
3
Loose, missing, or damaged gas cap
Low severity
A gas cap that doesn't seal is the single most common trigger for a large EVAP leak code; check for a cracked seal, missing cap, or cross-threading first.
Common cause
Parts:fuel filler cap
4
EVAP vent valve stuck open
Medium severity
A vent valve that won't seat lets the system bleed down instead of holding pressure/vacuum, which reads as a large leak.
Common cause
Parts:EVAP vent valve
5
EVAP purge valve failure
Medium severity
A purge solenoid stuck open provides a continuous path to atmosphere, which the monitor interprets as a large leak.
Common cause
Parts:purge valve
6
Cracked or split EVAP canister
Medium severity
A cracked canister housing is large enough to fail the monitor outright rather than intermittently.
Common cause
Parts:EVAP charcoal canister
7
Disconnected or split EVAP vapor hose
Medium severity
A hose that has popped off a fitting or split open is one of the most common large-leak findings on a smoke test.
Common cause
Parts:EVAP vapor hose
8
Corroded or perforated fuel tank/filler neck
Medium severity
Road-salt corrosion can perforate the tank or filler neck enough to produce a large, easily detected leak.
Common cause
Parts:fuel tank

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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