P0455 Evaporative Emission Control System Leak Detected (Gross Leak/No Flow)

P0455 indicates a large evaporative-emissions leak or no-flow condition. It is an EVAP-system leak-detection lead, not a direct part diagnosis.

Code details

Generic OBD-II · P0

System: Emissions
Code type: Generic (SAE / ISO controlled)
Standard: SAE J2012 / ISO 15031-6

Diagnostic boundary

A diagnostic trouble code reports that a monitored test failed. It does not prove one specific part is bad, and manufacturer logic can add vehicle-specific conditions.

Do not assume the gas cap is always the fault; a large leak can come from valves, hoses, seals, or damaged EVAP plumbing.

Symptoms of P0455

Check-engine light.
Sometimes a stronger fuel-vapour smell.
No drivability change.

Common causes of P0455

A missing, very loose, or failed fuel cap.
A disconnected or badly cracked EVAP hose.
A stuck-open vent or purge valve.
A damaged charcoal canister.

Useful checks before replacing parts

Check the fuel cap seal and installation first if the vehicle uses a serviceable cap.
Inspect EVAP hoses, purge and vent valves, filler-neck sealing, and tank-area connections.
Use smoke testing or the manufacturer leak-test procedure when visual inspection does not identify the leak.

Related OBD-II codes

These nearby emissions entries can help compare wording and pin down the fault area.