Evap vent control fault.
P0446 — also written PO446, P 0446, 0446 — is the OBD-II code for evap vent control circuit. Same code, same fix: this page covers every spelling of it.
This is the car’s computer telling you it can't vent the petrol tank's charcoal canister properly, usually because the solenoid at the back is seized or the wires have rotted through. Most common on Vauxhalls and older Toyotas that have seen a few too many salty Scottish winters.
P0446 is a emissions fault code, typically costing £80–£350 to put right in a UK garage.
What P0446 actually feels like to drive
- The 'Check Engine' light is staring you in the face but the car drives perfectly.
- A faint smell of petrol fumes around the rear wheel arch after a long run.
- The car is a nightmare to fuel—the petrol pump keeps clicking off every three seconds.
- A slight dip in idle speed when you're sat at the lights in town.
- The code keeps coming back exactly two drives after you’ve cleared it.
What causes P0446?
- Failed vent solenoid
- Wiring
UK vehicles that throw P0446 most often
- Vauxhall Corsa D/E 1.2 & 1.4 (2006-2019)
- Vauxhall Astra J / Insignia A (A14NET engine codes)
- Toyota Yaris 1.3 VVT-i (2005-2011)
- Nissan Qashqai J10 1.6 Petrol (2007-2013)
- Honda Civic 1.4/1.8 i-VTEC (2006-2012)
- Ford Fiesta 1.25 Zetec (2008-2017)
How P0446 is fixed
- Vent valve replacement
The P0446 misdiagnosis that wastes money
I’ve seen dozens of lads rush to swap the petrol cap or the purge valve under the bonnet because they're easier to reach. On this one, that’s usually a waste of money. P0446 is almost always an electrical issue with the vent solenoid tucked away near the charcoal canister at the back of the car. We get a lot of Vauxhalls where the wiring harness rubs against the subframe, causing a break. Slapping a fresh canister on without checking the 12v feed and ground at the plug is a rookie mistake I see far too often.
What a UK garage should charge for P0446
A diagnostic plug-in should cost you £40–£60 at a decent indie. If it’s just a broken wire, I’d charge an hour’s labour—maybe £70. If the solenoid is well and truly seized, a Bosch or Pierburg replacement part is usually £60 to £120 depending on the model. Fitting it is usually simple unless the bolts are rusted solid, so expect 30 to 60 mins labour. All in, you’re looking at £130–£220. Main dealers will likely double that, quoting 'unit replacement' for the whole canister assembly at £400 plus VAT.
P0446 repair cost in the UK
Most P0446 repairs land between £80–£350 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.
Bob's tip on P0446
If you're taking it to a local shop, ask the lad if they can 'command the vent valve' with their scan tool. If they just shrug, they're guessing with your wallet. A proper tech will click a button on their tablet, listen for the solenoid to click under the rear arch, and check the voltage. Also, don't let them tell you it's an MOT failure on a petrol car right away—it's an engine light (EML) which is a major fail if the car is post-2003, even if the emissions at the tailpipe are spot on. Check that wiring first; it’s usually just a £20 soldering job rather than a £150 part.
Can you drive with P0446?
Drivable.
Urgency: low.