P0499: Evaporative Emission System Vent Valve Control Circuit High
What to do
Driveable with no symptom. Will fail an emissions test.
What this code means
The vent valve control circuit is reading high — an open circuit, or a control wire finding a supply voltage. The mirror of the circuit-low fault. Corrosion having eaten through a conductor under the vehicle is the most common physical cause, so trace the harness along its route before condemning the valve.
Likely causes
Start here
- Road damage to underfloor wiring · moderate
- Open or shorted solenoid winding · moderate
- Broken wire in control circuit · moderate
- Corroded or loose connector · easy
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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