Powertrain, generic · Auxiliary emission controls

P0458 EVAP System Purge Control Valve A Circuit Low

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. P0458 means its control wire is shorted to ground: GM detects it with the driver off, when the line sits at ground instead of supply (20 of 25 samples, MIL after two trips); Saab's ME9 uses below 2.6 V at the output. The valve is then energised and open all the time, purging is uncontrolled – rough idle, rich mixture or hard starting after refuelling are possible.

Likely causes

Purge valve control wire chafed against ground
Purge valve coil shorted internally
Connector scorched or wet
Driver in the engine module

Symptoms

  • Check engine light on
  • Rough idle or rich mixture possible (valve permanently open)
  • Starting problems after refuelling possible

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

P0443P0459P0444P0445P0496

References: gsi.ext.gm.com, saabwisonline.com, static.nhtsa.gov.