Powertrain, generic · Fuel and air metering, auxiliary emission controls

P0039 Turbocharger/Supercharger Bypass Valve A Control Circuit Range/Performance

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

The turbocharger bypass valve A is the compressor recirculation (diverter) valve: it connects the pressure side of the compressor with the intake side upstream of the turbocharger. It opens when the throttle closes quickly at high boost, so the compressor does not surge and the compressor wheel keeps its speed for the next acceleration. It is not the wastegate, which bypasses exhaust gas around the turbine and has its own codes. The valve is either electric or a vacuum unit controlled by a solenoid. With P0039 the circuit is electrically intact, but the valve does not behave as commanded. On valves with a position sensor, for example, the valve must reach its rest position within a set time after being switched off; the code is set if the measured position deviates too far.

Likely causes

Valve sticking from carbon or oil mist, or diaphragm torn
Vacuum line or switching valve leaking (pneumatic design)
Position sensor in the valve faulty
Increased resistance in the wiring

Symptoms

  • Check engine light on
  • Fluctuating or too little boost
  • Loss of power
  • Fluttering noise when lifting off the throttle

Repair estimate

DifficultyMediumDIY possible
Parts and labour€80–400
Time0.5–2 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

turbocharger bypass valvebypass valve position sensorvacuum lines

Related codes

P0033P0034P0035P2261P00C3P0299

References: law.cornell.edu, gsi.ext.gm.com, ms-motorservice.com, en.wikipedia.org.