MasterTuning Fault code dictionary (DTC)

P0455 — Evaporative emission system: large leak

Severity: Informational Can you drive? Yes, no known limitation Make: All makes (OBD-II standard)
MeaningThe system that collects fuel tank vapours is not holding pressure. It does not affect how the engine runs, but it lights the warning lamp and fails the emissions test.
FamilyPowertrain (P)

Typical symptoms

Engine warning light on, with no other symptoms
Sometimes a fuel smell near the tank
Problems at the roadworthiness test

Common causes

Loose, dirty or hardened fuel cap seal: by far the most common cause
Cracked or disconnected vapour hose
Canister vent valve not closing
Damaged canister

What to do

Before anything else: tighten the fuel cap until it clicks and clear the code. A surprising number of cases end there. If it returns, a smoke test finds the hose or the valve.

Frequently asked questions

What does code P0455 mean?

Evaporative emission system: large leak. The system that collects fuel tank vapours is not holding pressure. It does not affect how the engine runs, but it lights the warning lamp and fails the emissions test.

Can I keep driving with code P0455 active?

Yes, no known limitation

Common causes — P0455

Loose, dirty or hardened fuel cap seal: by far the most common cause Cracked or disconnected vapour hose Canister vent valve not closing Damaged canister

How do you fix code P0455?

Before anything else: tighten the fuel cap until it clicks and clear the code. A surprising number of cases end there. If it returns, a smoke test finds the hose or the valve.

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