What does code P0456 mean on a Mercedes-Benz and is it safe to drive?
P0456: Evaporative Emission System Leak Detected (Very Small Leak). Here's what it means on your Mercedes-Benz, what usually causes it, what repairs typically cost, and how safe it is to keep driving.
What this code means
The EVAP system has detected a very small leak—often smaller than P0442. Commonly caused by a loose fuel cap or hairline crack in a hose.
Common causes for your Mercedes-Benz
- Loose or worn gas cap seal
- Hairline crack in EVAP hoses
- Minor leak at purge or vent valve fittings
Symptoms
- Check Engine Light only
- Usually no noticeable driving symptoms
Typical fixes
- Inspect and replace gas cap if seal is hardened or cracked
- Smoke-test EVAP system to locate tiny leaks
- Repair or replace leaking hoses and fittings
Repair cost range
For a Mercedes-Benz, repairs for P0456 often fall between $25 and $350, depending on the cause and whether you use OEM or aftermarket parts. Labor rates vary by location.
Known issues on Mercedes-Benz
Mercedes P0456 small EVAP leak is commonly the gas cap. Use OEM Mercedes caps—the thread specification differs from generic caps. If a new cap doesn't clear P0456, Mercedes's leak detection pump (LDP) can develop an internal diaphragm crack and is the next inspection point.
Most commonly affected models