P0039: Turbocharger/Supercharger Bypass Valve A Control Circuit Range/Performance
What to do
Driveable, though boost response will be poor. Avoid sustained full-throttle use until repaired.
What this code means
The bypass valve circuit is electrically sound but the valve is not achieving what it is asked to do. This is the code that catches mechanical failure the circuit codes miss: a torn diaphragm, a seized spindle, or a valve that no longer seals against boost pressure. Testing needs the valve actuated while boost is observed, not just a resistance check.
Likely causes
Start here
- Failed turbocharger bypass valve · moderate
- Torn bypass valve diaphragm · moderate
- Vacuum leak in intake manifold or hoses · moderate
Less common
- Carbon fouling of valve seat · moderate
- Intermittent wiring fault · moderate
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
Be the first to write this up
Nothing posted about this yet. Whatever you found is worth writing down — even a dead end saves someone the same afternoon.
What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
Sign in or create an account to add what you found about P0039.