EngineLightCodes
Powertrain code

P0459 EVAP System Purge Control Valve A Circuit High

Severity
Fix soon
Typical repair cost
$30–$220
Do it yourself
Possible, easy
Shop time
0.3–1.5 hours

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.

How the engine computer detects it

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.

Written from public technical sources and not yet checked by a mechanic. How we write these pages

Symptoms

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

Common causes

  1. Control wire shorted to battery voltage or supply Most likely
  2. Purge valve coil low-resistance (shorted turns) Possible
  3. Connector or harness damaged Possible
  4. Engine module Less likely

How to diagnose P0459

  1. Read every stored code with an OBD-II scanner. If misfire or fuel trim codes are there too, fix those first: they often cause this one.
  2. Inspect the parts involved: evap purge valve, purge valve wiring, engine control module.
  3. Work through the causes above from most to least likely, cheapest checks first.
  4. Clear the code and drive a full drive cycle to confirm the repair held.

Reading the code

P
Powertrain
0
Generic (SAE) code
4
Auxiliary emission controls
59
Specific fault

Questions drivers ask

Can I drive with code P0459?

Usually yes for a short time, if the car drives normally, the temperature gauge reads normal and the check engine light is steady. If the light flashes, the engine loses power or overheats, or other warning lights come on, pull over and have it checked.

Will my car pass an emissions inspection with P0459?

Probably not in states that test vehicles with an OBD-II scan: an emissions-related code that keeps the check engine light on is usually an automatic fail. Rules differ by state and county, so check yours.

Will P0459 clear by itself?

The light can go off after several drive cycles without the fault, but the code returns if the cause is still there. After a repair, the readiness monitors need a full drive cycle before an inspection.

Can I fix P0459 myself?

Often yes, with an OBD-II scanner and basic tools. Difficulty: easy. Start with the cheapest checks before replacing expensive parts.

This page is general information, not a substitute for a professional diagnosis. Repair costs are rough estimates for parts and labor and vary by vehicle and region.