AutoCodes – Generic – P004C

P004C Code - Turbocharger/Supercharger Boost Control 'B' Circuit Low

Quick Answer

The turbocharger has nozzle vane which opens and closes to control the volume of the exhaust gas flowing into the turbine. Common causes include Faulty boost pressure/ turbocharger position sensor, Boost pressure/ turbocharger position sensor harness is open or shorted, Boost pressure/ turbocharger position sensor circuit poor electrical connection. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means: P004C indicates Turbocharger/Supercharger Boost Control 'B' Circuit Low.
Common causes: Common causes include Faulty boost pressure/ turbocharger position sensor, Boost pressure/ turbocharger position sensor harness is open or shorted, Boost pressure/ turbocharger position sensor circuit poor electrical connection.
Severity: High - diagnose this code as soon as possible.
Can I drive?: Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

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Code Popularity 10,331

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Apr 07, 2019

Description
Possible Causes
How To Fix
Cost to Diagnose
Comments
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Code P004C Description

The turbocharger has nozzle vane which opens and closes to control the volume of the exhaust gas flowing into the turbine. This, in turn, controls the boost pressure, when the nozzle vane moves towards the closing direction, the pressure increases. When the vane moves towards the opening direction, the pressure decreases.

OBDII Code P004C - Turbocharger/Supercharger Boost Control 'B' Circuit Low - AutoCodes.com — P004C Code - Turbocharger/Supercharger Boost Control 'B' Circuit Low

What does this mean?

What are the Possible Causes of the DTC P004C?

Faulty boost pressure/ turbocharger position sensor
Boost pressure/ turbocharger position sensor harness is open or shorted
Boost pressure/ turbocharger position sensor circuit poor electrical connection
Faulty turbocharger/supercharger

How to Fix the DTC P004C?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P004C code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

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About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.