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P0455 Generic (SAE)

Evaporative Emission System Leak Detected (Gross Leak)

Updated 2026-10-02 · Auxiliary emission controls

Severity
Low
Typical repair cost
10 – 400 EUR
System
Powertrain

What it means

The EVAP system seals the fuel tank and routes vapours to the engine. During a self-test the module applies vacuum or pressure; if it cannot hold it at all, a gross leak is assumed.

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Symptoms

  • Check engine light, no driveability change
  • Fuel smell near the car
  • Slightly higher fuel consumption

Common causes

  1. Loose, worn or missing fuel cap
  2. Cracked EVAP hose
  3. Stuck open purge or vent valve
  4. Damaged charcoal canister
  5. Leaking filler neck

How to diagnose

  1. Tighten or replace the fuel cap and drive a few cycles
  2. Inspect all EVAP hoses for cracks
  3. Smoke test the EVAP system through the service port
  4. Command the vent valve closed with a scan tool and check it seals

Frequently asked questions

I just refuelled and P0455 appeared. Why?

Most often the fuel cap was not clicked shut or the seal is cracked. Tighten it and the code usually clears itself after a few drives.

Terms to know

EVAP system (evaporative emission control)Purge valve (EVAP purge solenoid)Charcoal canister (EVAP canister)Permanent code (PDTC)Smoke machine (leak detector)

Related codes

P0442P0456P0440P0446

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