P0499: Evaporative Emission System Vent Control Circuit High

What does P0499 mean?

P0499 is a diagnostic trouble code indicating "Evaporative Emission System Vent Control Circuit High". The ECU is reading a voltage that is above the expected range. This can be caused by a short to power in the wiring, a failed sensor, or a connector issue in the evap system.

Symptoms you may notice

• Check engine light (MIL) illuminated on dashboard
• Fuel smell near the vehicle
• Difficulty filling fuel tank
• Intermittent warning lights
• Erratic gauge readings

Common causes

• Damaged or corroded wiring harness
• Loose or disconnected electrical connector
• Failed evap system sensor or actuator
• Blown fuse in the related circuit
• Poor ground connection

What should you do?

This code sits in an engine peripheral, typically emissions or forced induction. It will not take braking or steering away, but it can put the car into limp mode, cost you fuel and fail a roadworthy. Book it in rather than clearing it and hoping.