P0499
EVAP System Vent Valve Control Circuit High
Same as P0498 with the control line open or shorted to supply. The evaporative system captures fuel vapor from the tank and purges it into intake; leaks or stuck purge valves leak hydrocarbons and cause emissions failures.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: easy
Symptoms
- Check engine light on
- Possible smell of fuel near tank or engine bay
- Failed emissions inspection
- Loose-cap warning may appear
Common causes
Ordered by how often each turns out to be the cause.
- Control line openCommon
- Control line shorted to supplyPossible
- Connector pins corroded - high contact resistanceLess likely
Parts involved
- EVAP Vent Valve
- EVAP Vent Wiring
P0499 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.