P0499 code meaning
EVAP System Vent Valve Control Circuit High
Powertrain system Generic code P04xx codes Check engine light
What P0499 means
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.
P0499 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyEasy, DIY possible
- Typical labor0.3 to 1.5 hours
- Clears after repairAfter a drive cycle
Symptoms of P0499
- Check engine light on
- EVAP readiness not set
- Usually no change in driving
Common causes of P0499
- Most 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
- Less likelyDriver in the engine module
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
EVAP vent valveVent valve wiringEngine control module
What each part of P0499 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 4 | Area: auxiliary emission controls (catalytic converter, EGR, EVAP). |
| 99 | The exact fault in that area. |
What to do next
- Note P0499 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0499
What does P0499 mean?
P0499 means "EVAP System Vent Valve Control Circuit High". 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. It is a generic code, so it means the same on every make.
Is it safe to drive with P0499?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P0499 fail an emissions test?
Yes, it can. P0499 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0499 to fix?
Difficulty: easy. A typical repair takes 0.3 to 1.5 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P0499 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.