P0459Generic code

P0459 Code: Evaporative Emission System Purge Control Valve Circuit High

The P0459 code indicates high voltage in the EVAP purge valve control circuit, from an open circuit or a short to voltage. Check the fuse, relay, connector and wiring before replacing the valve. The code usually does not affect driving much.

Severity
Low
Can I keep driving?
Yes, no immediate risk
Estimated cost
$30 to $200
Difficulty
Medium
System
Emissions Control
Applies to
All OBD2 vehicles

Updated Reviewed by Renzo Chacca

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What the P0459 code means

The purge valve opens the path for the vapors stored in the canister to flow into the intake, where they are burned. The computer opens and closes it with a pulsed signal.

The computer monitors the control circuit from its own driver transistor. The P0459 code indicates high voltage in the control circuit (an open circuit or a short to voltage). Before replacing the component, check the fuse, relay, connector and wiring, since they are the most common cause.

A valve that will not open keeps the canister from emptying (EVAP monitor incomplete). One that sticks open lets vapors and air into the engine all the time, causing hard starting after fueling and an unstable idle.

To confirm it, measure the continuity of each wire between the component connector and the computer connector with the key off. It should be less than 1 ohm, and an infinite reading means the wire is open. If the wiring is good, measure the component itself: infinite resistance confirms it is open inside.

P0459 code symptoms

  • Check engine light on.
  • Hard starting after fueling.
  • Unstable idle.
  • Gasoline smell.

Likely causes of the P0459 code

  1. Connector loose or broken. The most frequent cause, especially after another repair in the area.
  2. Open coil or motor, with infinite resistance in the component.
  3. Control wire cut between the component and the computer.
  4. Short to 12 V, where the control wire touches another wire that carries voltage.

How to diagnose the P0459 code step by step

  1. Command the component with the scan tool and check whether it responds.
  2. Check the fuse and relay.
  3. Measure the supply at the connector: battery voltage with the key on or when it is commanded.
  4. Measure the component resistance and compare it with the manual. Also check the insulation to ground.
  5. Check the control wire for continuity and for shorts.
  6. With the engine off, blow through the valve. No air should pass.
  7. Power it with 12 V or with the scan tool. It should open with a click.

How to fix the P0459 code

  • Repair the connector, the wiring or the power supply.
  • Replace the EVAP purge valve if it does not respond with correct power and control.
  • Clear the codes and verify that the monitor completes.

Technical reference data

  • 12 V solenoid with PWM control; approximate resistance 20 to 30 ohms.
  • Approximate values only: check the manufacturer data for your engine.

Brand-specific notes

This fault is very common on several manufacturers, and the purge valve is an inexpensive part.

P0459 on GM

Very common on GM vehicles, and the part is cheap.

P0459 on Ford

Very common on Ford vehicles, and the part is cheap.

P0459 on Toyota

Very common on Toyota vehicles, and the part is cheap.

P0459 on Hyundai

Very common on Hyundai vehicles, and the part is cheap.

Frequently asked questions about P0459

Can I drive with a P0459 code?
Yes. A P0459 code normally does not affect driving. Repair it before your emissions inspection.
What does the EVAP purge valve do?
The purge valve opens the path for the vapors stored in the canister to flow into the intake so they get burned. The computer opens and closes it with a pulsed signal.
Do I always have to replace the part?
No. Check the fuses, relays, connectors and wiring first.
How much does it cost to fix P0459?
Roughly $30 to $200, depending on whether it is wiring or the valve itself.
What does the P0459 code mean?
It is a generic OBD2 code that means the EVAP purge valve control circuit is reading high voltage, from an open circuit or a short to voltage.
What is the most common cause of P0459?
A loose or broken connector, especially after another repair in the area. An open valve coil or a cut control wire come next.

Related codes

Questions about the P0459 code

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