P0499EVAP System Vent Valve Control Circuit High
- 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 switched to ground by the module (GM scheme P0449/P0498/P0499; Ford uses P0446). P0499 means the control wire is shorted to positive: with the driver on the output stays high – GM sees 0.5 Ω or less to the supply, Saab above 4.6 V; MIL after two trips. The valve then cannot close, the system cannot be sealed, and the leak tests are suspended because they would otherwise report a large leak.
- What you may notice
- Check engine light on
- EVAP readiness not set
- Usually no change in driving
- Likely causes
- LikelyControl wire touching battery positive or the valve supply (chafed harness)
- PossibleVent valve coil with shorted turns, driver switches off
- PossibleMoisture or corrosion in the connector
- RareDriver in the engine module
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Easy · Often possible to do yourself.Typical cost: €30 – €250
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.