Loose, missing or improperly fitted gas cap. Non-original (non-conforming) gas cap. Other leak or damaged part in the EVAP system, such as a cut or disconnected hose. Damaged fuel tank filler neck, a split carbon canister, a defective vent or purge valve, a fuel tank sending-unit seal, a fuel tank pressure sensor, or a damaged fuel tank (listed by RepairPal).

Reseat or replace the gas cap. Repair cut or disconnected EVAP hoses. Repair other damaged EVAP components found by testing.

P0455🌫 Emissions / EVAPUsually OK to drive

P0455: Evaporative Emission (EVAP) System Leak Detected (large leak / no purge flow) (Meaning, Causes, Fixes)

Q: What does P0455 mean?

P0455 means the EVAP system has a large leak or no purge flow. The most common fix is the gas cap: reseat it, clear the code, and see if it comes back. The EVAP system stores fuel vapor in a charcoal canister and later purges it into the engine to be burned. P0455 means the PCM detected a large leak, or a lack of purge flow, in that system. Manufacturers word it slightly differently. For example, Chrysler says 'EVAP Large Leak Detected' and Nissan says 'canister purge system – gross leak'. RepairPal explains that it appears when the EVAP system can't build enough vacuum, usually because of an air leak.

Q: Can I keep driving with P0455?

Usually OK to drive. Generally safe to keep driving: you likely won't notice drivability problems. If you smell fuel, get it checked promptly.

Reviewed 2026-10-21 · Based on 3 cited source(s)

What P0455 means

The EVAP system stores fuel vapor in a charcoal canister and later purges it into the engine to be burned. P0455 means the PCM detected a large leak, or a lack of purge flow, in that system. Manufacturers word it slightly differently. For example, Chrysler says 'EVAP Large Leak Detected' and Nissan says 'canister purge system – gross leak'. RepairPal explains that it appears when the EVAP system can't build enough vacuum, usually because of an air leak.

Severity: can I keep driving?

Usually OK to drive

Generally safe to keep driving: you likely won't notice drivability problems. If you smell fuel, get it checked promptly.

Common symptoms

Check engine light on
Usually no drivability problems
Possibly a fuel smell or a vacuum noise near a leak

Likely causes

Roughly most to least common, based on the sources below. Your vehicle may differ.

Loose, missing or improperly fitted gas cap
Non-original (non-conforming) gas cap
Other leak or damaged part in the EVAP system, such as a cut or disconnected hose
Damaged fuel tank filler neck, a split carbon canister, a defective vent or purge valve, a fuel tank sending-unit seal, a fuel tank pressure sensor, or a damaged fuel tank (listed by RepairPal)

Diagnostic steps you can do

⚠ Before you start

Work on a cool engine, parked on level ground with the parking brake set. Never work under a car supported only by a jack.

Remove and reinstall the gas cap, clear the code, and drive for a day to see if it returns.
If it returns, replace the gas cap.
Inspect the EVAP hoses for cuts or holes. You may hear a vacuum noise or smell fuel near the leak.

Typical fixes

Reseat or replace the gas cap
Repair cut or disconnected EVAP hoses
Repair other damaged EVAP components found by testing

Repair costs vary widely by vehicle, region, parts brand and shop, so we don't quote prices. Get a written estimate after diagnosis.

🛠 When to call a pro

A new cap and visual inspection don't fix it: a smoke test will find the leak
Parts near the fuel tank need lifting the vehicle or lowering the tank

Where to buy

Plain search links. Always match parts to your exact year, make, model and engine.

OBD2 scanners on Amazon Parts at Advance Auto Parts catalog at RockAuto

FAQs

Why do I have both P0455 and P0442?

Both are EVAP leak codes for different leak sizes. Diagnose the system as a whole, starting with the cap and hoses.

Sources

Last reviewed 2026-10-21. Code definitions and repair steps can vary by manufacturer. Confirm with your vehicle's service information.