Powertrain, generic · Auxiliary emission controls
P0459 EVAP System Purge Control Valve A Circuit High
Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo
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.
Likely causes
Control wire shorted to battery voltage or supply
Purge valve coil low-resistance (shorted turns)
Connector or harness damaged
Engine module
Symptoms
- Check engine light on
- Fuel smell when the canister is full
- EVAP readiness not set
Repair estimate
DifficultyEasyDIY possible
Parts and labour€25–200
Time0.3–1.5 h
Typical range across vehicles; the real cost depends on what the testing finds.
Parts involved
evap purge valvepurge valve wiringengine control module
Related codes
References: gsi.ext.gm.com, saabwisonline.com, static.nhtsa.gov.