Powertrain, generic · Auxiliary emission controls

P0455 EVAP System Leak Detected - Large Leak

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

The evaporative emission (EVAP) system stores fuel vapour from the tank in a charcoal canister; a purge valve lets the engine draw it off, and a vent valve opens the canister to fresh air. P0455 means a large leak or that no vacuum builds up. Ford pulls the closed system down with engine vacuum and expects about −2 kPa within 30 s; after refuelling it sets P0457 instead. GM sets the code if 20 litres have been purged without reaching 2740 Pa tank vacuum (once per cold start, MIL after two trips). Saab's ME9 uses a pressure drop below 525 Pa. The code also covers blocked purging, for example a purge valve stuck closed.

Likely causes

Fuel cap missing, not clicked in or seal faulty (or capless flap)
Hose off or cracked (canister, filler neck, purge line)
Vent valve stuck open or purge valve stuck closed
Canister or filler neck cracked or corroded

Symptoms

  • Check engine light on (possibly a check fuel cap message)
  • Possibly fuel smell
  • EVAP readiness or emission inspection not passed

Repair estimate

DifficultyEasyDIY possible
Parts and labour€10–400
Time0.1–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

What to check first

  1. Check the fuel cap first
  2. Inspect hoses for disconnection
  3. Smoke-test the system

Parts involved

evap systemfuel capevap hosesevap purge valve

Related codes

P0442P0456P0457P0446P0496P0441

References: fordservicecontent.com, newtonnet.co.uk, gsi.ext.gm.com, saabwisonline.com.