P00C0: Turbocharger/Supercharger Bypass Valve B Control Circuit
What to do
Mention any fluttering or chattering noise when you lift off the accelerator after accelerating hard. That is the sound of air surging back through the turbocharger because this valve is not opening — it is a symptom rather than a desirable noise, and it is hard on the turbo's bearings.
Ask for the connector and wiring to be checked before the valve is replaced. It sits in a hot part of the engine bay where insulation hardens and terminals corrode.
Mention any recent work on the intake or turbocharger, since a connector left unplugged produces this exactly.
Do not leave it long. Repeated compressor surge shortens turbocharger life, and a turbo is considerably more expensive than a valve.
What this code means
An electrical fault has been detected in the second turbocharger bypass valve's control circuit.
A bypass or recirculation valve exists to deal with a specific problem: what happens to the air a compressor is still pushing when the throttle closes. Lift off at boost and the charge air has nowhere to go, so it stalls against the closed throttle and surges back through the compressor wheel. That is compressor surge, and it is audible as a flutter and destructive to the turbocharger's bearings.
The bypass valve opens at that moment and routes the air back to the compressor inlet, keeping it moving.
A second valve — B — means a second turbocharger, so this is a twin-turbo, a biturbo or a sequential system. Establish which cylinder bank or which stage it serves before diagnosing.
A control circuit code is electrical rather than mechanical. The usual three apply: a short to ground, a short to voltage, or an open — separated at the connector with the valve unplugged.
This valve lives on the hot side of the engine bay and its connector suffers accordingly. Heat-hardened insulation and corroded terminals are the ordinary findings, and the trivial case — left unplugged after intake or turbo work — is worth eliminating first.
Expect a flutter or chatter on lift-off if the valve is not opening, and treat that noise as a symptom rather than a characterful sound.
Likely causes
Start here
- Corroded or loose connector · easy
- Heat damage to wiring insulation · moderate
- Failed turbocharger bypass valve · moderate
Less common
- Open circuit in control wiring · moderate
- Sensor left disconnected after previous work · easy
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 P00C0.