P0499
Evaporative emission system vent valve control circuit high
The ECU has detected an abnormally high electrical signal in the EVAP vent-valve control circuit.
What this code means
The ECU has detected an abnormally high electrical signal in the EVAP vent-valve control circuit.
Possible causes
- Open circuit or poor connection
- Vent valve fault
- Short to voltage
- Control-module driver issue
Common symptoms
- Check engine light
- EVAP readiness monitor may fail
Checks to make
- Inspect vent-valve wiring and connector
- Check supply and control voltages
- Test vent valve according to manufacturer procedure
Safety
- Do not replace parts from the code alone. Confirm the fault with live data, wiring checks and manufacturer procedures. Keep clear of hot or moving engine components.
Model notes
The code definition is generic; exact diagnostic thresholds, component locations and repair procedures vary by vehicle.