Emissions control: EGR, DPF, catalytic converter and AdBlueGeneric OBD-II codeUrgency: Monitor
Code P0455: EVAP system: large leak detected
P0455 means: evaporative emission control system (EVAP): large leak detected.[1][2][3][4] The control unit has detected a large leak in the EVAP system, which collects petrol vapours from the tank into the canister and sends them to the intake to be burned. To check that it is sealed, it seals the system with the vent and purge valves and applies vacuum or pressure; P0455 is stored when the system does not hold for the required time. It is the serious version of P0442.[1][3]
What code P0455 means
The control unit has detected a large leak in the EVAP system, which collects petrol vapours from the tank into the canister and sends them to the intake to be burned. To check that it is sealed, it seals the system with the vent and purge valves and applies vacuum or pressure; P0455 is stored when the system does not hold for the required time. It is the serious version of P0442.[1][3]
AutoDTCs puts a large leak at an opening equivalent to a hole of more than 1 mm (0.040 inches); this is a figure from a single source. Mechanic Base clarifies that, although it is called a large leak, what the control unit measures is whether the system holds vacuum, and in rare cases the code may have nothing to do with the EVAP, so it recommends checking the manufacturer's meaning.[1][3]
It usually appears alongside P0456 (very small leak), which Samarins describes as very similar. On Volkswagen Group cars, Ross-Tech defines it as “large leak detected” and suggests checking the cap and the EVAP system.[2][4]
Original definition (SAE J2012): Evaporative Emission Control System Leak Detected (Large Leak)[1][2][3][4]
Causes of P0455
From most to least likely, according to the sources.
- 1Fuel cap loose, missing, damaged or with a broken seal. It is the most common cause and the first to check.[1][2][3][4]
- 2EVAP hose or pipe cracked, broken or disconnected between the tank and the canister.[1][2][3]
- 3Faulty vent valve (canister) or one stuck open.[1][2][3]
- 4Purge valve stuck open, keeping the system open during the test. Samarins adds that on Volkswagen and Audi the purge valve (N80) commonly causes this code, and also on Hyundai.[1][2][3]
- 5Canister with a cracked housing or damaged connection.[1][2][3]
- 6Filler neck with a damaged or corroded seal and, on cars with capless filling, a faulty filler unit.[1][2]
- 7Faulty leak detection unit, damaged tank pressure sensor or damaged tank.[2][3]
Symptoms
- Engine fault warning light on, usually with no driving symptoms.[1][2][3]Engine warning light: faults that cause it
- Smell of fuel, especially near the filler neck; more likely with a major leak.[1][2][3]Fuel smell: faults that cause it
- Loose fuel cap warning on the instrument panel, on cars that have one.[2]
- Difficulty filling the tank on some cars.[2]
- Possible slight increase in consumption, according to AutoDTCs.[1]Uses more fuel: faults that cause it
How to diagnose P0455
In order: from the most likely and cheapest to check to the most expensive.
- 1Check the cap: the seal must not be cracked or deformed and must close until it clicks or stops. Clear the code and complete an EVAP monitor driving cycle. If a new good-quality cap does not fix it, the leak is somewhere else.[1][2][3][4]
- 2Trace the visible hoses from the tank along the body to the canister and the purge valve: cracks, split seals, disconnected quick connectors and heat damage from the exhaust.[1][3]
- 3Carry out a smoke test, blocking the canister vent outlet. AutoDTCs indicates that large leaks usually show smoke within seconds.[1][2][3]
- 4Test the vent valve by applying battery voltage: it should click and close (it is normally open). With a bidirectional tool, command the vent to close and the purge to open while watching the system pressure: a vent that does not close, or a purge stuck open, prevents the system from holding vacuum.[1][2]
- 5Check that the purge valve is not fitted the wrong way round, as Ross-Tech points out for VW and Audi, and that the purge hose has no cracks.[2][4]
- 6Look for the manufacturer's technical bulletins for your model and this code: they may reveal a known fault or warranty coverage.[2][3]
- 7Read all the EVAP codes together, as they can narrow down the area. If there are too many, clear them and read again the ones that return after a driving test.[3]
Can I keep driving with P0455?
Monitor
AutoDTCs and Mechanic Base rate it as low severity: the car can be driven, but it is worth repairing before an emissions inspection, because vented petrol vapours are a polluting emission and the car would fail while the code is active. Mechanic Base makes one exception: a tank losing liquid fuel is a risk and must be repaired as soon as possible. Its author also never recommends driving with the warning light on, because a light that is already on does not warn of new faults.[1][3]
Documented faults related to P0455
Known faults of specific engines and cars, with their repair cost, the affected years and their sources.
Engine sensors: the most serious faults by engine and car
- High severityFrequency: Occasional2.0 DTI and 2.2 DTIVP44 injection pump and air mass meter failureGerman Wikipedia documents recurring failures of the Bosch VP44 injection pump and the air mass meter in the early years of this engine. An owner testimony for this engine describes the pump being replaced at 192,500 km, at a cost the owner calls «prohibitive».
- Medium severityFrequency: Common2.0 TDIClogged particulate filter or faulty pressure sensorThe 2.0 TDI's particulate filter clogs if the car mostly makes short journeys, because it never gets to regenerate; sometimes the fault is just the differential pressure sensor. Cleaning it costs around €200 and replacing it, €800 to €3,000.Repair (garage): €800–€3,000
- Medium severityFrequency: Common1.4 and 1.6 8vCrankshaft position sensor failure (TDC sensor)The crankshaft position sensor (capteur PMH, or TDC sensor) appears repeatedly in the reliability sources for the Clio II, the Kangoo I and the Dacia Logan I with this engine, with hard cold starting or stalling as the main symptoms. It is a cheap part, but the failure can leave you stranded.
- Medium severityFrequency: Common1.4 and 1.6 16vCrankshaft position sensor failureThe crankshaft position sensor (capteur PMH) appears repeatedly in the reliability sources for almost every generation with this engine, with hard cold starting, stalling or the car cutting out unexpectedly. It is a cheap part, but the failure can leave you stranded.
Frequently asked questions
Can I drive with code P0455?
Yes, according to the sources it does not affect driving or safety. It is worth repairing before an emissions inspection, and as soon as possible if there is a smell of liquid fuel or the tank is losing petrol.[1][3]
Does a new cap fix it?
Often it is the first thing that fixes it, but not always. AutoDTCs states that if a new good-quality cap does not clear the code, the leak is at another point and you should move on to the smoke test, the purge hose near the intake, the tank vent hose and the valves.[1]
Why did P0455 appear just after refuelling?
Mechanic Base explains that not tightening the cap properly, or refuelling with the engine running, can trigger the code; in those cases clearing it may be enough.[3]
What is the difference between P0455, P0442 and P0456?
They are all EVAP leaks detected by the control unit, and only the size changes. P0455 is the large leak; P0442, the small one; and P0456, the very small one. The exact thresholds depend on the manufacturer.[1][2][3]
Will I pass the MOT with code P0455?
If the code has switched on the engine warning light, no: with that light on, the inspection records a serious defect, and on Euro 5 and Euro 6 cars the ITV (Spain's roadworthiness inspection, similar to the MOT) also reads the OBD diagnostic system. Repair the fault before you go; clearing the code just before the inspection does not help either, because it counts as a serious defect.[5]
Not sure what is wrong with your car? Describe what you notice in the symptom diagnosis or see all fault codes.
Sources
Every fact on this page links to its source. If you find an error, let us know.
- P0455: Evaporative Emission System Leak Detected (Large Leak)AutoDTCs · Technical documentation · consulted 31 October 2026
- P0455 Evaporative Emission Control System Leak Detected (Large leak)Samarins.com · Technical documentation · consulted 31 October 2026
- P0455 – Evaporative Emission Control System (EVAP) Large Leak DetectedMechanic Base · Technical documentation · consulted 31 October 2026
- 16839/P0455/001109 - EVAP System: Large Leak DetectedRoss-Tech Wiki · Technical documentation · consulted 31 October 2026
- Desmontando mitos: ¿puede pasar mi coche la ITV con el testigo de «avería motor» encendido?Diariomotor · Motoring press · published 8 March 2021 · consulted 2 October 2026 · in Spanish