P0456 on a Toyota: 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 Toyota

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

Is P0456 common on Toyotas?

P0456 is one of the most common check engine codes on Toyotas, from the Camry and Corolla to the RAV4 and Highlander. An untightened or aging gas cap is the usual cause. On older Toyotas, a failing leak detection pump or cracked EVAP hoses can also set the code.

Commonly reported on: Camry, Corolla, RAV4, Highlander.

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 purge or vent valve
less common: Failing leak detection pump on older models

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 purge or vent valve	Yes	$30–120