P00C3

Turbocharger/Supercharger Bypass Valve A Control Circuit Low

P00C3 is a generic OBD-II powertrain diagnostic trouble code: Turbocharger/Supercharger Bypass Valve A Control Circuit Low. It is logged by the engine control unit when the powertrain monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.

Code
P00C3
Group
Powertrain
System
Powertrain
Severity
Warning (MIL on, possible limp mode)
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What P00C3 means

P00C3 is stored when the ECM detects that the control circuit voltage for Turbocharger or Supercharger Bypass Valve A is lower than expected. The bypass valve (sometimes called a diverter or recirculation valve in forced induction systems) is an electrically controlled solenoid that vents or recirculates compressed air under specific operating conditions such as throttle lift-off, to protect the turbocharger compressor from surge.

A low circuit condition typically indicates that the ECM output driver is seeing a voltage at or near ground when it expects a higher value, which can result from a short to ground in the wiring, an internally shorted solenoid coil, or a failed driver circuit inside the ECM. The valve itself may be stuck open or stuck closed depending on its default state, which can manifest as reduced boost pressure, compressor surge noise, or turbo lag.

Diagnosis requires verifying the wiring and connector condition first, then measuring solenoid coil resistance and comparing it to specification, before suspecting an ECM fault. Replacing the solenoid is the most common repair, but wiring faults between the ECM and the valve should always be ruled out first to avoid unnecessary part replacement.

Common causes

Most-frequently reported root causes when P00C3 is logged.

  • 1
    Short to ground in the wiring harness between the ECM and the bypass valve solenoid.
  • 2
    Failed bypass valve solenoid with an internally shorted coil.
  • 3
    Damaged wiring insulation causing intermittent or permanent short to chassis ground.
  • 4
    Corrosion or moisture ingress at the solenoid connector creating a low-resistance path to ground.
  • 5
    Failed ECM output driver circuit for the bypass valve control.
  • 6
    Incorrect aftermarket solenoid with wrong coil resistance causing an apparent low voltage condition.

Symptoms drivers notice

MIL illuminated.
Reduced turbocharger boost pressure.
Compressor surge or flutter noise on throttle lift-off.
Sluggish acceleration or turbo lag.
Possible intake system hissing or recirculation noise under boost.

How to diagnose P00C3

A typical diagnostic flow when this code is present.

  1. 1
    Connect a scan tool, record all DTCs, and check for associated boost pressure or throttle-related codes.
  2. 2
    Inspect the bypass valve solenoid connector and wiring for damage, corrosion, or chafing against hot or sharp surfaces.
  3. 3
    Disconnect the solenoid and measure coil resistance; compare to manufacturer specification.
  4. 4
    With the connector disconnected, check for voltage at the harness-side connector with ignition on to confirm the circuit is live and not shorted.
  5. 5
    Check for continuity from the solenoid signal wire to chassis ground to identify a wiring short.
  6. 6
    If wiring and solenoid resistance are within specification, check ECM supply voltage and grounds before suspecting ECM driver failure.
  7. 7
    Repair any wiring fault or replace the solenoid as indicated by test results, then clear codes and verify repair under load.

Related powertrain codes

Frequently asked questions

What is the difference between P00C3 (low) and P00C4 (high) for the same valve?

P00C3 indicates the control circuit voltage is too low, typically caused by a short to ground or shorted solenoid. P00C4 indicates voltage is too high, typically caused by an open circuit or short to voltage.

Can a stuck bypass valve cause boost-related codes as well as P00C3?

Yes. If the electrical fault prevents the valve from operating correctly, boost pressure deviation codes such as P0234 or P0299 may also be stored.

Is the bypass valve the same as a blow-off valve?

Functionally similar, but the bypass valve recirculates air back to the compressor inlet (closed-loop), while a blow-off valve vents to atmosphere. Both serve to protect the turbo from surge. SAE codes use the term bypass valve generically.

Will P00C3 cause the vehicle to enter limp mode?

On many turbocharged vehicles, yes. The ECM may limit boost pressure as a precaution when it cannot confirm bypass valve position, resulting in reduced power.

Disabling P00C3 in software

RaceTune can permanently disable P00C3 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.

Permanent
The monitor is disabled in the ECU itself — not just cleared. It cannot return.
Tailored to your file
Each patch is matched to your specific software version — never a one-size-fits-all file.
Reversible
The original file is always preserved. Reflash the stock to return the ECU to factory state.

Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.

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