P0455 fault code: Evaporative Emission System Leak Detected (large leak)

Last updated 19 August 2026 · OBDCode UK editorial

Self-drawn engine management light for P0455 EVAP large leak — Decorative labelled telltale: the engine management light that P0455 usually sets. Normally amber. This drawing is not manufacturer artwork and does not name any other lamp colour.

Can I drive with P0455? — Drive with care

Do not treat a large evaporative leak as normal driving. If you smell strong petrol in the cabin or see fuel on the ground, stop and keep ignition sources away. Otherwise drive only as far as needed to a garage.

P0455 means “Evaporative Emission System Leak Detected (large leak)” — an auxiliary emission controls fault in the powertrain. Drive with care. The computer has found a large leak in the petrol-vapour recovery system. Vapour is escaping before it can be stored and burned. This is an emissions leak, not an engine-failure warning on its own.

Can I DIY?

Caution — conditions apply. We do not publish DIY repair or strip-down steps for this code on this page. Read codes and observe only; leave the repair to a qualified garage.

Caution — conditions applyDIY boundary

ToolsBasic tools only — for example a household socket set, tyre gauge, or a consumer OBD reader.

Some checks may be possible for a careful DIY driver with the right tools and a safe place to work. Stop if anything feels beyond your skill or kit.

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For an AI assistant

Fault code: P0455 — Evaporative Emission System Leak Detected (large leak).
Can I drive: Drive with care. Do not treat a large evaporative leak as normal driving. If you smell strong petrol in the cabin or see fuel on the ground, stop and keep ignition sources away. Otherwise drive only as far as needed to a garage.
Question: What does this code mean for a UK car, is it safe to drive, what are the most likely causes, and what should I ask a garage to check before replacing parts?

For your garage

REPAIR BRIEF — prepared by the owner with obdcode.co.uk
Fault code: P0455 — Evaporative Emission System Leak Detected (large leak).
Drive guidance from obdcode.co.uk: Drive with care. Do not treat a large evaporative leak as normal driving. If you smell strong petrol in the cabin or see fuel on the ground, stop and keep ignition sources away. Otherwise drive only as far as needed to a garage.
Owner’s request: please diagnose before replacing parts, itemise diagnosis time separately, and quote before any work beyond diagnosis.

P04xxAuxiliary emission controls

MOT fail riskif the warning light stays on

What does P0455 mean?

P0455 is a generic (SAE standard) powertrain code reported by your car’s engine control unit. It sits in the P04xx block, which covers auxiliary emission controls. The stored description is “Evaporative Emission System Leak Detected (large leak)”. The code itself tells you which circuit or system tripped the fault — not always the exact part that failed.

How to diagnose P0455 yourself

Confirm P0455 and freeze-frame: Scan with an OBD-II reader while the car is stationary. Note whether P0455 is current or pending, and list every other stored code from the same scan. Stop if: You also have a flashing engine management light, a strong petrol smell in the cabin, or fuel on the ground.

Park safely and switch off before locating the socket. Its position varies, so use the vehicle handbook and never force or dismantle trim.
Check the filler cap clicks and seals: At the filler flap, with the car on its wheels, remove and refit the cap. It should turn until it clicks. Look at the rubber seal for cracks, flattening, or a missing cap. Stop if: The cap will not seat, fuel weeps from the neck, or you would need to raise the car to chase pipes.
Look at the filler flap area only: Stand beside the car. Check that the flap shuts, the cap is the type meant for this filler, and there is no obvious damage around the neck. Do not crawl under the vehicle. Stop if: You smell raw petrol strongly, see wet fuel, or feel you must go under the car.

Will P0455 fail an MOT?

If the engine management light is on, that is a Major defect at MOT (automatic fail) until the fault is repaired and the lamp stays off. P0455 is a vapour-leak flag, not an exhaust-catalyst test result.

Before booking your test, check what usually fails on your car: see our MOT pass rates by make and model, built from 33.1 million DVSA tests.

What the MOT data says

No MOT certificate item corresponds to this code; MOT outcome data cannot be shown.

P0400Exhaust Gas Recirculation Flow P0401Exhaust Gas Recirculation Flow Insufficient Detected P0402Exhaust Gas Recirculation Flow Excessive Detected P0403Exhaust Gas Recirculation Control Circuit P0404Exhaust Gas Recirculation Control Circuit Range/Performance P0405Exhaust Gas Recirculation Sensor 'A' Circuit Low P0406Exhaust Gas Recirculation Sensor 'A' Circuit High P0407Exhaust Gas Recirculation Sensor 'B' Circuit Low

P0455 — quick answers

Is it safe to drive with P0455?

Drive with care. Do not treat a large evaporative leak as normal driving. If you smell strong petrol in the cabin or see fuel on the ground, stop and keep ignition sources away. Otherwise drive only as far as needed to a garage.

Can I fix P0455 myself?

Caution — conditions apply. We do not publish DIY repair or strip-down steps for this code on this page. Read codes and observe only; leave the repair to a qualified garage. Basic tools only — for example a household socket set, tyre gauge, or a consumer OBD reader.

Will P0455 fail my MOT?

Fault-code identifiers are standard diagnostic facts. Their explanations and diagnostic guidance on this site are original editorial summaries, not reproduced SAE wording. MOT defect rules reflect the DVSA MOT inspection manual (2026). This page is general guidance for UK drivers, not a substitute for a professional diagnosis.