P0455 on a Mercedes-Benz: Causes, Fixes & Repair Cost

🟢 Low severity · drivable

Safe to drive — this is an emissions leak, not an engine problem, but fix it before your next emissions test.

What P0455 means on a Mercedes-Benz

On a Mercedes-Benz, P0455 means the engine computer has detected a large leak in the evaporative emission (EVAP) system, so fuel vapors are escaping. On Mercedes models, a loose or damaged gas cap is the most common trigger, though a failing purge valve or a cracked vent line can also cause it.

Is P0455 common on Mercedes-Benzs?

P0455 appears on Mercedes models like the C-Class, E-Class, and GLE, usually on older cars. The gas cap is the cheapest thing to check first, and a smoke test will locate anything beyond that.

Commonly reported on: C-Class, E-Class, GLE, GLC.

Symptoms

Check engine light is on
Possible fuel smell
No driving symptoms
Emissions test failure

Common causes

most common: Loose, missing, or damaged gas cap
common: Disconnected or cracked EVAP hose
common: Faulty EVAP purge valve
less common: Crack in the charcoal canister

How to fix it

Fix	DIY?	Typical cost
Tighten or replace the gas cap	Yes	$10–30
Inspect and reconnect or replace cracked EVAP hoses	Yes	$10–80
Have a smoke test performed to find the exact leak	Mechanic	$80–180
Replace a faulty purge valve	Mechanic	$150–350