Evaporative Emission Control System Leak Detected (gross leak)
P0455 indicates the evaporative emission control (EVAP) system has detected a large leak or loss of purge flow. This system prevents fuel vapors from escaping into the atmosphere, and the code triggers when the engine computer detects a significant malfunction in pressure or flow.
What You Might Notice
- Check engine light illuminated
- No noticeable drivability issues or performance loss
- Possible fuel odor near the vehicle
- May notice gas cap is loose or missing
- No changes in fuel economy or engine operation
Most Common Causes
- 1
Loose or missing gas cap
The most common cause is a loose, missing, or improperly sealed fuel door cap. Even a slightly loose cap breaks the EVAP system seal and triggers the code.
- 2
Non-OEM or damaged gas cap
An aftermarket, damaged, or worn gas cap that no longer seals properly can cause large EVAP leaks. The cap must be manufacturer-original to ensure proper sealing.
- 3
EVAP hose cracks or disconnection
Rubber hoses in the EVAP system can crack, split, or disconnect from age, heat exposure, or physical damage, causing large vapor leaks.
- 4
Charcoal canister or purge control valve failure
The charcoal canister stores fuel vapors or the purge control valve that releases them can crack, fail, or malfunction, preventing proper system operation.
How to Diagnose It
- 1
Check Loose or missing gas cap — The most common cause is a loose, missing, or improperly sealed fuel door cap. Even a slightly loose cap breaks the EVAP system seal and triggers the code.
- 2
Check Non-OEM or damaged gas cap — An aftermarket, damaged, or worn gas cap that no longer seals properly can cause large EVAP leaks. The cap must be manufacturer-original to ensure proper sealing.
- 3
Check EVAP hose cracks or disconnection — Rubber hoses in the EVAP system can crack, split, or disconnect from age, heat exposure, or physical damage, causing large vapor leaks.
- 4
Check Charcoal canister or purge control valve failure — The charcoal canister stores fuel vapors or the purge control valve that releases them can crack, fail, or malfunction, preventing proper system operation.
How to Fix It
- 1
Inspect and reseat gas cap
Remove the fuel door cap and inspect for cracks, damage, or debris. Clean the cap and fuel filler neck threads, then reinstall the cap firmly until it clicks. Clear the code and test drive to confirm resolution.
- 2
Replace gas cap
If the cap is damaged, worn, or non-OEM, replace it with a genuine manufacturer gas cap. Ensure it is the correct type for your vehicle model and seals completely.
- 3
Inspect EVAP hoses and connections
Visually inspect all EVAP system hoses, connections, and clamps under the hood and beneath the vehicle for cracks, splits, disconnections, or deterioration. Reconnect any loose hoses or replace damaged sections.
- 4
Replace charcoal canister or purge valve
If hoses and cap are intact, the charcoal canister or purge control valve may be faulty. Use a smoke test to pinpoint the exact leak location, then replace the defective component.
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