P0455 moderate

Evaporative Emission Control System Leak Detected (Large Leak)

The P0455 code means the vehicle's onboard diagnostic system has detected: Evaporative Emission Control System Leak Detected (Large Leak). This is a moderate severity code.

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Keep driving?: Yes, but fix soon
DIY difficulty: medium
Estimated cost: $5-$30 for gas cap; $80-$200 for vent valve; $200-$500 for filler neck

Try This First ($8 Fix)

Stant 10838 OE Fuel Cap

A cracked or loose gas cap causes 60%+ of EVAP codes. This $8 replacement clears P0442, P0455, and P0457 more often than any other repair.

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Find the Leak

THIKPO Automotive Smoke Machine

If a new gas cap does not clear it, the leak is somewhere in the EVAP plumbing. A smoke machine finds the exact leak -- a cracked hose, bad seal, or stuck vent valve -- in minutes instead of guessing at parts.

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Clear the Code

ANCEL AD310 OBD-II Scanner

Clear the code after the repair. If the light stays off after 50 miles, you just saved $200+ in shop fees.

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Common Symptoms

Check Engine Light on
Strong fuel odor near the vehicle
Possible emissions test failure

Probable Causes (Ranked by Likelihood)

Missing or severely damaged gas cap Very High
Disconnected or broken large EVAP hose High
Failed or stuck-open vent valve High
Cracked or split fuel filler neck Moderate
Damaged charcoal canister Moderate

Step-by-Step Diagnostic Procedure

Verify the gas cap is present and properly seated with an undamaged seal.
Visually trace all large EVAP hoses (3/8 in or larger) from the fuel tank to the charcoal canister and to the engine.
Command the vent valve closed with a scan tool and monitor fuel tank pressure: pressure should hold if the system seals.
Perform a smoke test with the vent blocked to locate the large leak. A large leak will be immediately visible.
Inspect the filler neck where it attaches to the fuel tank for cracks or loose clamps.

Common Fixes by Vehicle

What techs usually find when diagnosing P0455 on specific vehicles — tap your vehicle for the fix and the exact part:

2004-2017 Toyota Tacoma/4Runner easy (cap) DIY

Loose or damaged gas cap is the most common cause. If the cap is tight and code returns, check the EVAP charcoal canister under the truck -- road debris damages it. Also check the vapor pressure sensor on the fuel tank. Toyota TSB 0116-08 covers EVAP system diagnosis on trucks.

Labor: 5 min (cap), 1 hour (canister)

Common fix part Stant OE Fuel Cap View on Amazon→ Compare fitment at PartsGeek→

2007-2018 Jeep Wrangler JK 3.6L/3.8L easy DIY

EVAP purge valve failure is extremely common. Located on the intake manifold, easily accessible. Mopar 4891738AB. Also check the gas cap seal -- Wranglers get a lot of dust/dirt that degrades the cap seal faster. After any off-roading, inspect EVAP lines under the body for damage.

Labor: 20 min

Common fix part Dorman EVAP Purge Solenoid View on Amazon→ Compare fitment at PartsGeek→

2009-2020 Chevrolet Silverado/Sierra 5.3L easy DIY

Check the EVAP vent solenoid mounted near the charcoal canister behind the rear axle. GM TSB #16-NA-043. The solenoid sticks open, causing a large leak detection. ACDelco 214-2149 is the OE replacement. Also inspect the EVAP line from the tank to the canister for rust-through.

Labor: 30 min

Common fix part ACDelco EVAP Vent Solenoid View on Amazon→ Compare fitment at PartsGeek→

2008-2019 Nissan Rogue/Pathfinder 2.5L moderate DIY

The EVAP leak detection pump (mounted near the charcoal canister) fails on Nissan vehicles around 80-100K miles. The pump motor burns out and cannot pressurize the system for self-test. Dorman 310-222 is the aftermarket replacement. Access is under the vehicle near the fuel tank.

Labor: 1 hour

Common fix part Dorman EVAP Leak Detection Pump View on Amazon→ Compare fitment at PartsGeek→

Frequently Asked Questions

What is the difference between P0442 and P0455?

P0442 indicates a small leak (less than 0.040 in diameter) while P0455 indicates a large leak (greater than 0.080 in). A large leak is often as simple as a missing gas cap.

Is P0455 an emissions or safety issue?

Primarily emissions. The larger concern is the fuel odor, which represents raw hydrocarbon vapors. These are flammable and should be addressed promptly, especially near heat sources.