Powertrain, generic · Auxiliary emission controls

P0447 EVAP System Vent Control Circuit Open

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

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. P0447 belongs to the older scheme for the vent valve circuit (P0446 circuit, P0447 open, P0448 shorted), used by Subaru (also in the Saab 9-2X), VW and Nissan; GM reports an open vent circuit as P0449, Ford as P0446. On Subaru the valve is fed from the main relay and switched to ground by the module; if the voltage at the module output is missing or the coil is high-resistance (nominal 10–100 Ω), the code sets after two consecutive drives. The valve stays in its rest position and the leak test cannot run.

Likely causes

Vent valve connector corroded or off (underbody, splash water)
Vent valve coil open (resistance outside 10–100 Ω)
Wire to the module or supply from the main relay open
Engine module or its connector

Symptoms

  • Check engine light on
  • EVAP leak test does not run, readiness not set
  • Usually no change in driving

Repair estimate

DifficultyEasyDIY possible
Parts and labour€30–250
Time0.3–1.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

evap vent valvevent valve wiringengine control module

Related codes

P0446P0448P0449P0498P0499

References: saabwisonline.com, static.nhtsa.gov, static.nhtsa.gov.