P0455 on a 2016 Chevrolet Silverado 1500

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 2016 Chevrolet Silverado 1500

Ranked from 792 NHTSA owner complaints filed for this vehicle.

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1
Cracked fuel pump/sending-unit module at the top of the tank
High severity
Four service records document the in-tank fuel pump module's outlet port cracking and leaking fuel in the same spot across multiple trucks - a large enough compromise of the tank's sealed integrity to fail a large-leak test.
Reported in 4 NHTSA complaints
Parts:fuel pump module
2
Fuel tank vapor vent leak requiring tank replacement
High severity
An EVAP-leak-detected code was traced by the dealer to the fuel tank leaking at its internal vents, requiring full tank replacement; a leak of this size is consistent with a large/gross leak code as well.
Reported in 1 NHTSA complaint
Parts:fuel tank
3
Damaged fuel filler neck/spout retaining clip
Medium severity
A broken filler-port retaining clip leaves the fuel spout loose and unsealed, a plausible large-leak path at the filler end of the system.
Reported in 1 NHTSA complaint
Parts:fuel filler neck assembly
4
Missing, loose, or damaged gas cap
Low severity
Still the most common trigger for a large EVAP leak code fleet-wide.
Common cause
Parts:gas cap
5
Disconnected or split EVAP hose/line
Medium severity
A fully separated or badly split vapor line produces an easily detected large leak.
Common cause
Parts:EVAP hose
6
Damaged or rusted fuel tank (general wear, distinct from the module-leak pattern above)
High severity
Corrosion or physical damage to the tank itself is a classic large-leak source on higher-mileage trucks.
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