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All codes/P004C

P004C

Turbocharger/Supercharger Boost Control B Circuit Low

High severity

Boost control B circuit voltage below expected range. Same as P0047 on actuator B. Boost control tracks commanded vs. actual manifold pressure; persistent deviation means wastegate, vanes, hose or actuator are not delivering the requested pressure.

Boost control B circuit voltage below expected range. Same as P0047 on actuator B. Boost control tracks commanded vs. actual manifold pressure; persistent deviation means wastegate, vanes, hose or actuator are not delivering the requested pressure.

Common causes

  • Wiring shorted to ground

    One of the most commonly reported causes for this code — check this first.

    high

    Typical part cost: $90-660

  • Connector pins corroded - high contact resistance

    Less common, but worth ruling out after the more likely causes.

    low

    Typical part cost: $90-660

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First things to check

  1. 1Confirm the code with a scan tool and check for additional related codes.
  2. 2Inspect the relevant sensors, wiring, and connectors for damage or corrosion.

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Tools you may need

Already have a compatible scanner? Use it. If not, a Bluetooth OBD2 adapter can help you confirm engine codes and check supported live sensor data before replacing parts.

Illustration of a Bluetooth OBD2 adapter, not a product photo

Basic checks

Veepeak OBDCheck BLE

A Bluetooth LE adapter for reading standard engine codes and supported live data.

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Illustration of a Bluetooth OBD2 adapter, not a product photo

Regular diagnostics

vgate iCar Pro BLE 4.0

A Bluetooth LE adapter with an automatic sleep feature for routine code and sensor checks.

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Illustration of a Bluetooth OBD2 adapter, not a product photo

Another option

OBDLink CX

A Bluetooth LE adapter to consider when comparing supported vehicles and diagnostic apps.

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Illustrations shown, not product photos. Check vehicle, phone and app compatibility before buying. These adapters do not guarantee access to ABS, airbags or manufacturer-specific systems. Clearing a code does not repair the fault and can reset emissions readiness monitors.

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Related codes

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Frequently asked questions

What does P004C mean?

P004C means "Turbocharger/Supercharger Boost Control B Circuit Low". It is a generic OBD-II code that points to a fault in the fuel & air metering / auxiliary emission controls.

What are the most common causes of P004C?

wiring shorted to ground; connector pins corroded - high contact resistance; harness chafing through insulation — these are the most commonly reported causes. Verify with a proper diagnosis before replacing parts, or use the Wrenchify app for a vehicle-specific diagnosis.

Can I keep driving with this code?

This code can put the vehicle into limp or reduced-power mode. Avoid extended driving and have the vehicle diagnosed promptly. Use the Wrenchify app for a full diagnosis specific to your vehicle.

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