P0039Turbocharger/Supercharger Bypass Valve A Control Circuit Range/Performance
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- 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.
- What you may notice
- Check engine light on
- Fluctuating or too little boost
- Loss of power
- Fluttering noise when lifting off the throttle
- Likely causes
- LikelyValve sticking from carbon or oil mist, or diaphragm torn
- PossibleVacuum line or switching valve leaking (pneumatic design)
- PossiblePosition sensor in the valve faulty
- RareIncreased resistance in the wiring
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €80 – €400
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.