P0446EVAP System Vent Control Circuit
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- The evaporative emission (EVAP) system stores fuel vapour from the tank in a charcoal canister; a purge valve lets the engine draw it off, and a vent valve opens the canister to fresh air. The vent valve is normally open and closes for the leak test. By its wording P0446 is its control circuit, and Ford uses it that way for open and shorted circuits. GM, however, uses P0446 for vent system performance – a blocked vent path: while purging with the vent valve open, the tank must not build up vacuum; more than 2989 Pa for 5 s before 4 litres have been purged sets the code, MIL after two trips. GM reports vent circuit faults as P0449, P0498 and P0499. A blocked vent makes refuelling difficult.
- What you may notice
- Check engine light on
- Refuelling problems, nozzle clicks off early (blocked vent)
- Hissing when opening the fuel cap (vacuum)
- EVAP leak test does not run
- Likely causes
- LikelyVent valve or filter blocked by dirt, dust or water (GM reading)
- PossibleVent valve electrically faulty, coil open or shorted (Ford reading)
- PossibleConnector or wire to the vent valve corroded or open
- PossibleCanister clogged with charcoal or liquid (overfilling)
- RareVent hose kinked or blocked by an insect nest
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €40 – €400
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.