OBD-II code · Powertrain (generic)
P004C Turbocharger/Supercharger Boost Control B Circuit Low
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.
Is it safe to drive with P004C?
The car may go into limp mode (reduced power). Get it diagnosed before a long trip.
Common causes
- Most likelyWiring shorted to ground
- Less likelyConnector pins corroded - high contact resistance
- Less likelyHarness chafing through insulation
Symptoms
- Charge status indicator shows fault
- Charging may not start or interrupts
- Slower-than-expected charge rate
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Often, with basic tools
- Typical labour
- 0.5–3 h
- Emissions test
- Likely to fail
- After the fix
- A drive cycle is needed before the light stays off
- Parts involved
- Boost Control Solenoid B, Actuator Wiring
Related codes
- P0047Turbocharger/Supercharger Boost Control A Circuit Low
- P0049Turbocharger/Supercharger A Turbine Overspeed
- P004ATurbocharger/Supercharger Boost Control B Circuit/Open
- P004BTurbocharger/Supercharger Boost Control B Circuit Range/Performance
- P004DTurbocharger/Supercharger Boost Control B Circuit High
- P004ETurbocharger/Supercharger Boost Control A Circuit Intermittent/Erratic
- P004FTurbocharger/Supercharger Boost Control B Circuit Intermittent/Erratic
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.