Powertrain, generic · Auxiliary emission controls

P0498 EVAP System Vent Valve Control Circuit Low

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. The vent valve is normally open and switched to ground by the module; P0449 (open), P0498 and P0499 form the newer code scheme for its circuit, used mainly by GM and Saab models with GM engines, while Ford uses P0446. P0498 means the control wire is shorted to ground: GM sees 0.5 Ω or less to ground with the driver off (20 of 25 samples), Saab below 2.6 V – MIL after two trips. The valve is then permanently energised and closed, so the tank is not vented and refuelling becomes difficult.

Likely causes

Vent valve control wire chafed against ground (underbody, tank area)
Vent valve coil shorted internally
Corrosion or water in the connector
Driver in the engine module

Symptoms

  • Check engine light on
  • Refuelling difficult, nozzle clicks off
  • Vacuum noise when opening the fuel cap

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

P0449P0499P0446P0447P0448P0458

References: gsi.ext.gm.com, saabwisonline.com, law.cornell.edu.