What does P0456 mean?
The computer found a very small EVAP leak, roughly the size of a 0.020-inch hole. These are the hardest to find and are often a fuel cap seal or a tiny hose crack.
Codes are a starting point. They tell you which test failed, not which part to replace. Check for other stored codes and fix those in a sensible order.
Symptoms
- Check engine light
- Possible fuel smell
- Hard starting after refueling (with purge problems)
- No change in how the car drives in most cases
Common causes
- Worn fuel cap seal
- Hairline crack in a hose or fitting
- Leaking vent or purge valve seal
How to diagnose P0456
- Check the fuel cap and its seal first.
- Run a smoke test, the most reliable way to find EVAP leaks.
- Command the purge and vent valves with a scan tool and check that they open and seal.
- Inspect the filler neck and hoses under the vehicle.
How to fix it
- Replace the fuel cap
- Replace cracked hoses
- Replace the purge or vent valve
- Replace the charcoal canister or filler neck
Estimated repair cost
Likely repairs for P0456 run from about $15 to $700, depending on the cause.
| Repair | Typical range (parts + labor) |
|---|---|
| Fuel cap replacement | $15 - $45 |
| EVAP smoke test | $100 - $200 |
| EVAP purge valve | $100 - $300 |
| EVAP vent valve/solenoid | $100 - $350 |
| Charcoal canister replacement | $250 - $700 |
These are rough US estimates for an independent shop in 2026, based on typical parts prices and standard labor times. Dealers, big trucks, luxury brands and high-cost areas often run higher. They are not quotes. Use the repair cost estimator to adjust for your vehicle.
How serious is P0456?
Low severity
Safe to drive. It will fail an emissions test until fixed.
P0456 FAQ
Is P0456 worth fixing?
It does not hurt the engine, but it will keep the check engine light on and can fail an emissions test. A new OE fuel cap is the cheap first step.
What does P0456 mean?
P0456 stands for "Evaporative Emission System Leak Detected (Very Small Leak)". The computer found a very small EVAP leak, roughly the size of a 0.020-inch hole.
Can I drive with a P0456 code?
Safe to drive. It will fail an emissions test until fixed.
How much does it cost to fix P0456?
It depends on the cause. The likely repairs for P0456 range from about $15 to $700 at an independent shop in the US, plus a diagnostic fee of roughly $100-$200. These are rough estimates; dealer prices and some vehicles run higher.
What is the most common cause of P0456?
The most common causes are: worn fuel cap seal; hairline crack in a hose or fitting; leaking vent or purge valve seal.