The evap vent valve is stuck shut, so the tank cannot breathe properly. You may notice a hiss when opening the filler cap or slow filling at the pump.
P2422 — also written P2422, P 2422, 2422 — is the OBD-II code for evaporative emission system vent valve stuck closed. Same code, same fix: this page covers every spelling of it.
P2422 is a emissions fault code, typically costing £80–£450 to put right in a UK garage.
What causes P2422?
- Vent valve seized with road dirt
- Blocked charcoal canister
- Water or spider ingress into the vent line
- Wiring fault
How P2422 is fixed
- Replace the vent valve
- Inspect and replace the charcoal canister if saturated
- Clear the vent line
P2422 repair cost in the UK
Most P2422 repairs land between £80–£450 including parts and labour. The spread is wide because the cheap fix (a sensor, a hose, a leak) and the expensive fix (a major component) throw the same code — which is why a proper diagnosis before parts are bought saves the most money.
Can you drive with P2422?
Yes, but the light will fail an MOT on newer cars.
Urgency: low.
What P2422 is telling you
Emissions codes are logged when the ECU's own monitors cannot prove the aftertreatment system is doing its job. The light is the result of a plausibility test failing, not of a part reporting itself broken, which is why the fault is so often in the measuring circuit rather than the component being measured.
On P2422 specifically — evaporative emission system vent valve stuck closed — the stored code records the moment that check failed, not the moment the part gave up. That gap is why two cars with the same code can need completely different repairs.
How P2422 is diagnosed properly
Each of the known causes is ruled in or out in cost order, cheapest and most likely first. On P2422 that means working through them like this:
- Vent valve seized with road dirt — commanded on and off with the diagnostic tool while its current draw and movement are watched, which separates a stuck part from a dead circuit.
- Blocked charcoal canister — measured as a pressure or flow difference across the component, so a partial restriction is not mistaken for a clear one.
- Water or spider ingress into the vent line — opened, inspected for green corrosion and spread pins, and back-probed rather than unplugged, so the reading is taken with the circuit live.
- Wiring fault — checked with the loom flexed and the engine warm, because a wiring fault that is intermittent when cold shows itself under heat and vibration.
An hour of diagnostic time on P2422 routinely saves more than it costs, because the alternative is buying the most expensive part on that list and hoping.
The repairs that actually clear P2422
- Replace the vent valve
- Inspect and replace the charcoal canister if saturated
- Clear the vent line
After the repair the code is cleared and the car is driven until the relevant readiness monitor completes, rather than handed back as soon as the light goes out. A code that has only been erased will come straight back on the next drive cycle.
What happens if P2422 is ignored
This is not an emergency, but it is not a code to clear and forget either. It will return, and while it is stored the ECU is running a fallback value rather than a measured one.
For reference, P2422 typically lands at £80–£450 all-in at an independent garage in the UK — main-dealer quotes for the same job usually sit above that.
Getting P2422 looked at
Bob's Mechanical Repairs is an independent garage in Birnam, Dunkeld, Perthshire, with 32 years of Bob's experience on the tools. If P2422 is showing on your car, bring the scan results with you — we will read the live data ourselves, tell you which of the causes above it actually is, and price the repair before any work starts.