P0456 on a Chevy: Causes, Fixes & Repair Cost

🟢 Low severity · drivable

Safe to drive — this is a tiny emissions leak, not an engine problem. Fix it before your next emissions test.

What P0456 means on a Chevy

On a Chevy, P0456 means the evaporative emission (EVAP) system has a very small leak. The system still runs, but your vehicle will fail an emissions test until the leak is found, and an untightened gas cap is the most common trigger.

Is P0456 common on Chevys?

P0456 is common on Chevy models like the Silverado, Equinox, and Malibu, and an under-tightened gas cap is the most common cause. On higher-mileage models, a cracked EVAP hose or failing vent valve is often the culprit. The system is sensitive, so even a tiny leak sets the code.

Commonly reported on: Silverado, Equinox, Malibu, Tahoe.

Symptoms

Check engine light on
Usually no other symptoms
Occasional faint fuel smell

Common causes

most common: Gas cap not fully tightened or seal worn out
common: Tiny crack in an EVAP hose or O-ring
common: Failing EVAP vent or purge valve
less common: Very small crack in the canister or filler neck

How to fix it

Fix	DIY?	Typical cost
Tighten or replace the gas cap	Yes	$10–30
Inspect and replace cracked EVAP hoses	Yes	$10–60
Have a smoke test performed to find the exact leak	Mechanic	$50–150
Replace a faulty vent or purge valve	Yes	$30–150