Powertrain, generic · Auxiliary emission controls

P0448 EVAP System Vent Control Circuit Shorted

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. P0448 is the short-circuit code of the older scheme for the vent valve. Subaru (also in the Saab 9-2X) expects supply voltage above 10 V at the module output with the valve off; a short to positive or a coil below 1 Ω sets the code after two drives, and Subaru then also replaces the module, as its driver may be damaged. Nissan and Infiniti use P0448 differently, for a vent valve or vent path stuck closed by dust or water, with replacement of canister, valve and filler tube. GM and Ford do not use the code.

Likely causes

Vent valve or vent path blocked by dust, dirt or water (Nissan reading)
Vent valve coil shorted (below 1 Ω)
Control wire shorted to positive
Module driver damaged

Symptoms

  • Check engine light on
  • Refuelling problems if the vent is blocked
  • EVAP leak test does not run

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–700
Time0.5–3 h

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

Parts involved

evap vent valvevent valve wiringcharcoal canisterengine control module

Related codes

P0446P0447P0449P0498P0499P0452

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