P0440: Evaporative Emission Control System Malfunction
Low SeveritySafe to drive (short-term)EVAP System
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.
Estimated repair costFrom €10 to €600+, varies by vehicle
What does P0440 mean?
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.
What are the symptoms of P0440?
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
What causes P0440?
Here are the most common causes of P0440, ranked by how likely they are to be the culprit:
highLoose, damaged, or missing fuel cap
highCracked or disconnected EVAP hose
mediumFailed purge or vent valve
mediumCracked or saturated charcoal canister
lowDamaged fuel tank or filler neck seal
Is it safe to drive with P0440?
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.
How do you diagnose P0440?
Follow these steps to pinpoint the root cause of P0440:
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
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
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
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
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
How much does P0440 cost to fix?
Repair costs for P0440 vary depending on the root cause and your vehicle. Here are typical estimates:
Repair
Parts Cost
Labor Cost
Total Estimate
DIY Difficulty
Replace fuel cap
€10–€40
€0–€0
€10–€40
Easy
Replace vent or purge valve
€40–€150
€30–€80
€70–€230
Moderate
Replace charcoal canister
€100–€400
€80–€200
€180–€600
Professional
Prices estimated as of March 2026. Costs vary by region, vehicle, and shop.
P0440 on specific vehicles
P0440 behaves differently depending on your vehicle. Select your car below for model-specific causes, known issues, and adjusted cost estimates:
P0440 on BMW 3 Series
BMW 3 Series • 2005–2024
BMW uses a leak detection pump (LDP) mounted near the charcoal canister to actively test the EVAP system. A failing LDP is a frequent cause of false P0440 codes on the E90 and F30. The fuel tank vent valve on the E90 is also a known failure point. Newer BMW models use a capless filler neck, so check the flapper assembly if no other leak is found.
What causes P0440 on a BMW 3 Series?
BMW 3 SeriesFailed leak detection pump on E90/F30 triggering false code
BMW 3 SeriesFuel tank vent valve failure
P0440 repair cost for BMW 3 Series
Estimated costs for BMW 3 Series ownersadjusted higher than average due to BMW-specific parts pricing
Repair
Parts Cost
Labor Cost
Total Estimate
DIY Difficulty
Replace fuel cap
€14–€56
€0–€0
€14–€56
Easy
Replace vent or purge valve
€56–€210
€42–€112
€98–€322
Moderate
Replace charcoal canister
€140–€560
€112–€280
€252–€840
Professional
Prices estimated as of March 2026. Costs vary by region, vehicle, and shop.
P0440 on Volkswagen Golf
Volkswagen Golf • 2005–2024
The Mk5 and Mk6 Golf with the N80 purge valve have a well-known failure where the valve sticks open or closed, triggering P0440. The charcoal canister on Mk6 models can crack from underbody road salt exposure. Always tighten the bayonet-style fuel cap until you hear the click.
What causes P0440 on a Volkswagen Golf?
Volkswagen GolfN80 purge valve sticking on Mk5/Mk6 (chronic failure)
Volkswagen GolfCharcoal canister cracks from road salt exposure
P0440 repair cost for Volkswagen Golf
Estimated costs for Volkswagen Golf ownersadjusted higher than average due to Volkswagen-specific parts pricing
Repair
Parts Cost
Labor Cost
Total Estimate
DIY Difficulty
Replace fuel cap
€12–€46
€0–€0
€12–€46
Easy
Replace vent or purge valve
€46–€173
€35–€92
€81–€265
Moderate
Replace charcoal canister
€115–€460
€92–€230
€207–€690
Professional
Prices estimated as of March 2026. Costs vary by region, vehicle, and shop.
P0440 on Audi A4
Audi A4 • 2005–2024
The B7 and B8 A4 with the 2.0 TFSI EA888 engine commonly trigger P0440 due to the N80 purge valve clicking loudly and failing in the open position. The valve is mounted on the intake manifold and is replaceable in under 30 minutes. A loud ticking from the engine bay is the classic symptom before the code sets.
What causes P0440 on a Audi A4?
Audi A4N80 purge valve clicking and failing on B7/B8 2.0 TFSI
Audi A4Brittle EVAP hoses near the engine from heat cycling
P0440 repair cost for Audi A4
Estimated costs for Audi A4 ownersadjusted higher than average due to Audi-specific parts pricing
Repair
Parts Cost
Labor Cost
Total Estimate
DIY Difficulty
Replace fuel cap
€13–€50
€0–€0
€13–€50
Easy
Replace vent or purge valve
€50–€188
€38–€100
€88–€288
Moderate
Replace charcoal canister
€125–€500
€100–€250
€225–€750
Professional
Prices estimated as of March 2026. Costs vary by region, vehicle, and shop.
P0440 on Ford Focus
Ford Focus • 2005–2024
The Focus Mk2 and Mk3 use a screw-type fuel cap with a rubber seal that hardens over time. A worn cap seal is the most common cause of P0440 on this model. The purge valve on the 1.6 Ti-VCT and 1.0 EcoBoost is accessible from the top of the engine, making it an easy DIY replacement.
What causes P0440 on a Ford Focus?
Ford FocusWorn fuel cap seal on Mk2/Mk3 (most common cause)
Ford FocusCarbon buildup on purge valve from 1.6 Ti-VCT/1.0 EcoBoost
P0440 repair cost for Ford Focus
Estimated costs for Ford Focus ownersadjusted lower than average due to Ford-specific parts pricing
Repair
Parts Cost
Labor Cost
Total Estimate
DIY Difficulty
Replace fuel cap
€9–€36
€0–€0
€9–€36
Easy
Replace vent or purge valve
€36–€135
€27–€72
€63–€207
Moderate
Replace charcoal canister
€90–€360
€72–€180
€162–€540
Professional
Prices estimated as of March 2026. Costs vary by region, vehicle, and shop.
Related diagnostic codes
These codes are often seen alongside P0440 or indicate related issues:
Yes. Any active OBD-II code with the check engine light on causes an automatic fail at EU vehicle inspections (TÜV in Germany, ITV in Spain, TA in Lithuania, SKP in Poland). You must clear the underlying fault before retesting.
Can a loose fuel cap really trigger P0440?
Yes, and it is the most common cause. The EVAP system is sealed, so even a small gap at the cap allows vapours to escape and the ECU registers a leak. Always tighten the cap until it clicks. Replace it if the rubber seal is cracked or compressed.
How long until P0440 clears after I fix it?
Once you tighten or replace the fuel cap, it takes 3 to 5 complete drive cycles for the ECU to retest the EVAP system and clear the code automatically. A drive cycle includes a cold start, mixed driving, and shutdown. You can also clear it manually with a scan tool.
What is the difference between P0440 and P0442?
P0440 is the generic EVAP malfunction code, often the first one set when the ECU detects something is wrong. P0442 specifically indicates a small leak (under 1mm equivalent orifice). Many vehicles set both codes together, with P0442 being more specific about the leak size.
