P0459: EVAP System Purge Control Valve A 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. Purge valve A is switched to ground by the module and fed from the main relay. P0459 means its control wire is shorted to positive, detected with the driver switched on, when the line should sit at ground (GM 20 of 25 samples, MIL after two trips; Saab ME9 above 4.6 V). The valve then cannot open, the canister is not purged and fills up; the driver protects itself and the leak tests are suspended.

Low severity. Can I keep driving?Yes, you can normally keep driving. If there is a strong smell of gasoline, find the leak before continuing and do not smoke nearby.

Symptoms

Check engine light on
Fuel smell when the canister is full
EVAP readiness not set

Most likely causes

Control wire shorted to battery voltage or supply
Purge valve coil low-resistance (shorted turns)
Connector or harness damaged
Engine module

What to check, in order

Start with the simplest. You can tick off each step.

Start with the fuel cap: tighten it fully and check its seal
Check the sensor's ground and make sure the signal wire is not receiving voltage from another circuit.
Inspect the hoses and connections around the tank and the charcoal canister
Use the scanner to test the purge and vent solenoid valves
Run a smoke test to find small leaks

Good to know

Repair difficulty: easy
It affects emissions.

What each character of P0459 means

P: Powertrain: engine and transmission
0: Generic code: same on every make
4: Emissions
59: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0459?

Yes, you can normally keep driving. If there is a strong smell of gasoline, find the leak before continuing and do not smoke nearby.

What causes code P0459?

The most common causes are: control wire shorted to battery voltage or supply; purge valve coil low-resistance (shorted turns); connector or harness damaged.

Related codes

Sources

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.