P0442: Evaporative Emission System Leak Detected (Small Leak)
Low SeveritySafe to drive (short-term)EVAP System
P0442 means the engine control unit has detected a small leak in the evaporative emission control system. This system captures fuel vapours from the tank and routes them to the engine to be burned. A small leak allows vapours to escape, increasing hydrocarbon emissions.
What does P0442 mean?
P0442 means the engine control unit has detected a small leak in the evaporative emission control system. This system captures fuel vapours from the tank and routes them to the engine to be burned. A small leak allows vapours to escape, increasing hydrocarbon emissions.
P0442 is a evap system-related diagnostic trouble code classified as low severity. When your vehicle's ECU detects this condition, it stores P0442 and illuminates the check engine light.
What are the symptoms of P0442?
If your vehicle has triggered P0442, you may notice one or more of these symptoms:
Check engine light on
Faint fuel smell near the vehicle, especially in warm weather
Failed emissions test
No noticeable driveability symptoms in most cases
Fuel cap warning light on some vehicles
What causes P0442?
Here are the most common causes of P0442, ranked by how likely they are to be the culprit:
highLoose, damaged, or missing fuel cap
highCracked or deteriorated EVAP hoses
mediumFaulty purge valve (stuck open)
mediumLeaking charcoal canister
lowDamaged fuel tank filler neck or seal
Is it safe to drive with P0442?
Generally yes, for short-term driving. A small EVAP leak does not affect engine performance or safety. You can drive normally, but repair before your next emissions inspection. A loose fuel cap is the most common cause.
How do you diagnose P0442?
Follow these steps to pinpoint the root cause of P0442:
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 a few days to see if it returns
Visually inspect all EVAP hoses from the fuel tank to the charcoal canister and from the canister to the purge valve at the engine. Look for cracks, loose clamps, or disconnections
Perform a smoke test on the EVAP system by sealing the system and introducing smoke. Watch for smoke escaping at hose connections, the canister, or the fuel tank area
Test the purge valve and vent valve with a scan tool by commanding them open and closed. A stuck-open purge valve can allow ambient air into the system, mimicking a leak
If the smoke test reveals no external leaks, inspect the charcoal canister for cracks and the fuel tank for damage, particularly around the fuel pump module seal
How much does P0442 cost to fix?
Repair costs for P0442 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 EVAP hose(s)
€10–€60
€40–€150
€50–€210
Moderate
Replace purge valve or vent valve
€20–€100
€30–€120
€50–€220
Moderate
Replace charcoal canister
€60–€250
€60–€200
€120–€450
Moderate
Prices estimated as of March 2026. Costs vary by region, vehicle, and shop.
P0442 on specific vehicles
P0442 behaves differently depending on your vehicle. Select your car below for model-specific causes, known issues, and adjusted cost estimates:
P0442 on Volkswagen Golf
Volkswagen Golf • 2003-2024
The Golf Mk5 and Mk6 have a known issue with the N80 purge valve sticking, which can trigger P0442. The EVAP hoses routed under the vehicle near the fuel tank are also susceptible to damage from road debris. VW fuel caps use a bayonet-style lock that must be turned until it clicks.
What causes P0442 on a Volkswagen Golf?
Volkswagen GolfN80 purge valve sticking open or closed
Volkswagen GolfEVAP hose damage from road debris under the vehicle
P0442 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
€11–€44
€0–€0
€11–€44
Easy
Replace EVAP hose(s)
€11–€66
€44–€165
€55–€231
Moderate
Replace purge valve or vent valve
€22–€110
€33–€132
€55–€242
Moderate
Replace charcoal canister
€66–€275
€66–€220
€132–€495
Moderate
Prices estimated as of March 2026. Costs vary by region, vehicle, and shop.
P0442 on BMW 3 Series
BMW 3 Series • 2006-2024
BMW vehicles use a leak detection pump (LDP) to test the EVAP system. A failing LDP can falsely trigger P0442 even when there is no actual leak. The fuel tank vent valve on E90 models is also a known failure point. BMW caps are capless on some newer models.
What causes P0442 on a BMW 3 Series?
BMW 3 SeriesFailing leak detection pump giving false positive
BMW 3 SeriesFuel tank vent valve failure on E90 models
P0442 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
€13–€52
€0–€0
€13–€52
Easy
Replace EVAP hose(s)
€13–€78
€52–€195
€65–€273
Moderate
Replace purge valve or vent valve
€26–€130
€39–€156
€65–€286
Moderate
Replace charcoal canister
€78–€325
€78–€260
€156–€585
Moderate
Prices estimated as of March 2026. Costs vary by region, vehicle, and shop.
P0442 on Ford Focus
Ford Focus • 2005-2022
The Focus uses a vacuum-based EVAP monitoring system. The purge valve on the 1.6 Ti-VCT and 2.0 GDI engines is mounted on the intake manifold and can develop carbon buildup causing it to stick. The fuel cap on European models is a standard screw-type.
What causes P0442 on a Ford Focus?
Ford FocusPurge valve carbon buildup on 1.6 Ti-VCT/2.0 GDI
Ford FocusCracked EVAP hose near the charcoal canister
P0442 on Toyota Yaris
Toyota Yaris • 2006-2024
P0442 on the Yaris is most commonly caused by a worn fuel cap seal, as the cap is a simple screw-type design. The EVAP system on Toyota vehicles is very reliable and rarely develops hose or canister issues. A new cap almost always resolves the code.
What causes P0442 on a Toyota Yaris?
Toyota YarisWorn fuel cap seal
Toyota YarisCharcoal canister saturation from fuel tank overfilling
P0442 repair cost for Toyota Yaris
Estimated costs for Toyota Yaris ownersadjusted lower than average due to Toyota-specific parts pricing
Repair
Parts Cost
Labor Cost
Total Estimate
DIY Difficulty
Replace fuel cap
€9–€34
€0–€0
€9–€34
Easy
Replace EVAP hose(s)
€9–€51
€34–€128
€43–€179
Moderate
Replace purge valve or vent valve
€17–€85
€26–€102
€43–€187
Moderate
Replace charcoal canister
€51–€213
€51–€170
€102–€383
Moderate
Prices estimated as of March 2026. Costs vary by region, vehicle, and shop.
Related diagnostic codes
These codes are often seen alongside P0442 or indicate related issues:
Yes. A loose, cracked, or missing fuel cap is the most common cause of P0442. The EVAP system is sealed, and even a slight gap at the cap allows vapours to escape. Always tighten the cap until you hear it click and replace it if the seal is worn.
What is the difference between P0442 and P0455?
Both indicate EVAP system leaks, but P0442 is a small leak (less than about 1mm equivalent orifice) while P0455 is a large leak. Small leaks are often from deteriorated hoses or a worn cap seal. Large leaks suggest a disconnected hose or missing cap.
Will P0442 go away on its own?
If the cause was a loose fuel cap and you tighten it properly, the ECU will eventually clear the code after several successful EVAP system tests during normal driving. This may take 3-5 drive cycles. You can also clear it with a scanner.
Is P0442 serious?
It is not mechanically serious and will not damage your engine or affect performance. However, it means fuel vapours are escaping into the atmosphere, and the check engine light will cause a failed emissions inspection in any EU country.
How does the EVAP system detect a small leak?
Most modern vehicles use either a vacuum-based test or a dedicated leak detection pump. The system seals itself and applies a slight vacuum or pressure, then monitors whether it holds. A small drop indicates a leak, and the ECU sets P0442.
