P0455 on a GMC: Causes, Fixes & Repair Cost

🟢 Low severity · drivable

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

What P0455 means on a GMC

On a GMC, P0455 means the EVAP system has a large leak and fuel vapors are escaping. The truck or SUV will still run and drive normally, so the check engine light is usually the only sign. It's an emissions issue, not a drivability issue.

Is P0455 common on GMCs?

P0455 is a fairly common EVAP code on GMC trucks and SUVs like the Sierra, Yukon, Terrain, and Acadia. GM's EVAP system uses a purge valve on the engine and a vent valve near the fuel tank, and these can stick open. A loose gas cap is still the first thing to check.

Commonly reported on: Sierra, Yukon, Terrain, Acadia.

Symptoms

Check engine light is on
Possible faint fuel smell
Usually no driving symptoms

Common causes

most common: Loose, missing, or damaged gas cap
common: Stuck-open EVAP purge valve
common: Cracked or disconnected EVAP hose
less common: Faulty vent valve or cracked 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	$15–80
Have a smoke test performed to find the exact leak	Mechanic	$50–150
Replace a stuck purge valve or faulty vent valve	Yes	$40–160