What usually causes P0455?

Filler cap missing or loose, disconnected hose.

VAG 16839EVAP system leak detected (large leak)

16839 is the VW Group 5-digit number VCDS (and older VAG-COM versions) shows for P0455. P0455 means “EVAP system leak detected (large leak)”. It's a generic powertrain code (auxiliary emission controls), so it means the same on every make, including VW, Škoda, Audi, SEAT and Cupra.

Not urgent
SystemEmissions
TypeGeneric (same on all makes)
VCDS number16839

How urgent is it?

Usually not urgent; often emissions-related.

Which system and module

Scanline files it under Emissions. The first letter, P, means powertrain (engine, transmission, emissions).

Usually stored by the engine control unit (VCDS address 01, Engine).

What usually causes it

Filler cap missing or loose
disconnected hose

Typical causes are a starting point, not a diagnosis of your car.

Related codes

Got this code on your car?

Paste your whole scan into Scanline to see which faults are current and which are old news. It runs in your browser; nothing is uploaded.

Open Scanline

Scanline explains fault codes; it isn't a repair authority. This page explains what the code means; it can't tell you what is wrong with your car. Ross-Tech's wiki has their own notes on VW Group faults.