P0440

Evaporative Emission Control System Malfunction

OBD-II diagnostic trouble code P0440indicates a fault detected by the vehicle's onboard computer. This code applies to all OBD-II compliant vehicles and should be addressed promptly to avoid potential engine or emissions system damage.

Severity Level 3 — Moderate

This code indicates a moderate issue that may affect vehicle performance and fuel economy. Continued driving is possible in most cases, but prompt diagnosis and repair are recommended to prevent further damage.

Common Symptoms

• Check Engine Light on
• Fuel odor from rear of vehicle
• Hissing sound from fuel tank area after engine shutdown
• No significant driveability issues on most vehicles
• May fail emissions test

Possible Causes

• Loose or faulty gas cap — always check first, most common and cheapest fix
• Faulty EVAP purge control valve — stuck open causing continuous vacuum draw
• Faulty EVAP vent control valve — stuck closed, unable to complete system test
• Cracked or disconnected EVAP vacuum hose or vapor line
• Faulty charcoal canister — saturated with fuel from overfilling tank repeatedly
• Damaged fuel tank pressure sensor

Common Fixes

• Tighten or replace gas cap ($10-30)
• Replace EVAP purge valve ($50-200)
• Replace EVAP vent valve ($60-250)
• Smoke test to locate and repair EVAP hose/vapor leak ($100-200 diagnostic + parts)
• Replace charcoal canister ($200-600)

Estimated Repair Cost

These are estimated costs based on generic repair data. Actual costs may vary depending on your vehicle, location, and labor rates.

Explore Repair Costs

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