Will P0440 fail my emissions test?

A stored emissions code with the check engine light on is the kind of defect that gets a car rejected, but there is no single European test: each country sets and grades its own. Clear the underlying fault and let the readiness monitors complete before you retest.

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.

P0440: Evaporative Emission Control System Malfunction

Quick Answer

Safe to drive (short-term)

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.

Severity: Low · EVAP System
Estimated repair cost: From €10 to €600+, varies by vehicle

Scan your own car in about 60 seconds: see whether P0440 is really what it has, how urgent it is, and what the fix should cost. Free on iPhone and Android with an ELM327 adapter (Bluetooth LE on iPhone).

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What does P0440 mean?

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.

Where it is on the car

Fuel filler cap
Fuel tank pressure sensor
Charcoal canister
Vent valve (to fresh air)
Purge valve
Intake manifold and engine

A leak can be anywhere in this system: the cap, a hose, the canister or a valve. The cap and the vapour hoses are marked. The cap is the cheapest and quickest thing to check first.

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:

Loose, damaged, or missing fuel cap
: high
Cracked or disconnected EVAP hose
: high
Failed purge or vent valve
: medium
Cracked or saturated charcoal canister
: medium
Damaged fuel tank or filler neck seal
: low

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 a lit check engine light with a stored emissions code is what gets a car rejected at inspection, so address it 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 50 to 120 EUR for the diagnostic alone at a workshop
Check the purge and vent valves: with manufacturer-level software you can command them open and closed and listen for clicking (a generic OBD2 reader cannot run these actuator tests); otherwise test them off the car with 12 V and a hand vacuum pump. 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.

Full repair guides

EVAP Purge Valve Replacement Cost

P0440 on specific vehicles

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

P0440 on BMW

BMW 3 Series

See BMW-specific causes & cost

P0440 on Volkswagen

Volkswagen Golf

See Volkswagen-specific causes & cost

P0440 on Audi

Audi A4

See Audi-specific causes & cost

P0440 on Ford

Ford Focus

See Ford-specific causes & cost

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

Common questions about P0440

Will P0440 fail my emissions test?: A stored emissions code with the check engine light on is the kind of defect that gets a car rejected, but there is no single European test: each country sets and grades its own. Clear the underlying fault and let the readiness monitors complete before you retest.
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.

Read our detailed guides

Scan your car with Skanyx to diagnose P0440

Your car logged P0440. Skanyx reads it on a standard OBD2 adapter (Bluetooth LE on iPhone), tells you whether it is safe to keep driving, and shows the €10-€600 repair range so you know the number before a shop quotes you. Free on iPhone and Android, and you do not need to be a mechanic to read it.