P0459: Evaporative Emission System Purge Control Valve Circuit High
The EVAP purge valve circuit shows a voltage above its normal range.
Normal risk
Safe to drive. Have it checked at the next opportunity.
Short answer · Can I keep driving with P0459?
Yes. Driving is usually not affected. Have the valve and wiring checked.
What does P0459 mean?
Code P0459 means the engine control unit sees a high voltage in the purge valve control circuit, from an open control wire, a short to voltage or a failed valve.
What the car does when the code is set
The check engine light comes on. The engine may start with difficulty right after refuelling and idle unevenly, because extra fuel vapour enters the intake. Fuel trims may also become strongly negative.
How the system works
The purge valve sits between the charcoal canister and the intake manifold. When the engine runs under the right conditions, the engine control unit opens it in pulses so the engine can draw in and burn the stored fuel vapour. When the valve is closed, no vapour should reach the engine. The control unit checks this by watching the tank pressure or the fuel trims while it commands the valve closed. If vapour still flows, it stores a high purge flow code.
Common symptoms
Possible causes
Listed without ranking. The cause on your car depends on make, engine and mileage — see the maker notes below.
- Purge valve stuck openThe valve does not close, so vapour flows into the intake all the time.
- Wiring faultA short in the control circuit keeps the valve open.
- Saturated or damaged canisterCharcoal particles can block or damage the valve.
How it is diagnosed
- Test the valve with the engine offDisconnect the valve and blow or apply vacuum through it: with no power, most purge valves should be closed.
- Check engine behaviour after refuellingHard starting or rough idle right after refuelling is typical for a purge valve stuck open.
- Check the wiringMake sure the valve is not permanently powered or grounded.
- Replace the valveClear the code and let the system run its self-test again.
Questions about P0459
Can a new purge valve fix P0459?
Only if the valve is the cause. Measure the valve coil and check the control wire first.
Why is my car hard to start after filling up?
A purge valve stuck open lets fuel vapour into the intake while refuelling, which floods the engine for the next start.
Can a stuck purge valve damage the canister?
Over time, liquid fuel can reach the canister and saturate the charcoal. That is why it should be fixed soon.