P0440: Evaporative Emission Control System Malfunction

P0440 is the generic OBD-II code for an evaporative emission control system malfunction. It means the ECU detected a fault in the system that captures fuel vapours from the tank and routes them to the engine. The most common trigger is a loose or missing fuel cap, but it can also indicate hose leaks, a failed purge valve, or a cracked charcoal canister.

P0440 is a evap system-related diagnostic trouble code classified as low severity. When your vehicle's ECU detects this condition, it stores P0440 and illuminates the check engine light.

If your vehicle has triggered P0440, you may notice one or more of these symptoms:

• Check engine light illuminated
• Faint fuel odour around the vehicle, especially in warm weather
• Possible failed emissions test
• No noticeable driveability issues in most cases
• Fuel cap warning indicator on some vehicles

Here are the most common causes of P0440, ranked by how likely they are to be the culprit:

Generally yes, for short-term driving. P0440 is a generic EVAP fault and does not affect driveability. You can drive normally, but the check engine light will cause an automatic failure at any EU vehicle inspection. Address before your next emissions test.

Follow these steps to pinpoint the root cause of P0440:

1. Check the fuel cap first. Remove it, inspect the rubber seal for cracks or debris, and re-seat it until it clicks. Clear the code and drive for several cycles to see if it returns
2. Visually inspect EVAP hoses from the fuel tank to the charcoal canister and from the canister to the purge valve at the engine. Look for cracks, brittle plastic, loose clamps, or disconnections
3. Perform a smoke test on the EVAP system. Seal the system, introduce smoke, and watch for visible plumes escaping at hose connections, the canister, or the fuel tank area. Expect 40 to 100 EUR for the diagnostic alone at a workshop
4. Use a scan tool to command the purge valve and vent valve open and closed. Listen for clicking. A stuck-open or stuck-closed valve is a frequent cause
5. If the smoke test reveals no external leaks, inspect the charcoal canister for cracks and check the fuel tank pressure sensor reading with live data

Repair costs for P0440 vary depending on the root cause and your vehicle. Here are typical estimates:

P0440 behaves differently depending on your vehicle. Select your car below for model-specific causes, known issues, and adjusted cost estimates:

These codes are often seen alongside P0440 or indicate related issues: