P0440 on a Mercedes-Benz: Causes, Fixes & Repair Cost

🟢 Low severity · drivable

Safe to keep driving — it is a general emissions-system fault, not an engine problem — but have it fixed before your next emissions test.

What P0440 means on a Mercedes-Benz

On a Mercedes-Benz, P0440 means the engine computer found a general problem in the evaporative emission (EVAP) system that stores fuel vapors from the tank. It is the catch-all EVAP code, less specific than the leak-size codes P0442, P0455, and P0456, so it often appears with other EVAP codes. The car typically drives exactly as it should.

Is P0440 common on Mercedes-Benzs?

P0440 is common on Mercedes vehicles as the EVAP hoses and valves age, particularly the rubber lines under the hood and the vent plumbing around the fuel tank at the rear. A loose gas cap is still one of the first things to check on this brand. It is an emissions concern, not a mechanical failure.

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

Symptoms

Check engine light on
Possible faint fuel smell
No drivability changes

Common causes

most common: Cracked or aged EVAP hoses near the engine
common: Loose, missing, or failing gas cap
common: Faulty purge valve
less common: Leak at the fuel filler neck seal

How to fix it

Fix	DIY?	Typical cost
Tighten or replace the gas cap	Yes	$10–30
Replace cracked EVAP hoses	Yes	$20–80
Smoke test the EVAP system to locate the leak	Mechanic	$50–150
Replace the purge valve	Yes	$80–200