OBD-II code · Powertrain (generic)
P004B Turbocharger/Supercharger Boost Control B Circuit Range/Performance
Boost control B mechanical/hydraulic deviation from target. Same as P0046 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 P004B?
The car may go into limp mode (reduced power). Get it diagnosed before a long trip.
Common causes
- Most likelyVacuum/boost line leak
- Less likelySensor element aged beyond calibration window
- Less likelySensor mounting loose - signal damping
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
- Best left to a mechanic
- Typical labour
- 1–6 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, Wastegate B
Related codes
- P0046Turbocharger/Supercharger Boost Control A Circuit Range/Performance
- P0048Turbocharger/Supercharger Boost Control A Circuit High
- P0049Turbocharger/Supercharger A Turbine Overspeed
- P004ATurbocharger/Supercharger Boost Control B Circuit/Open
- P004CTurbocharger/Supercharger Boost Control B Circuit Low
- P004DTurbocharger/Supercharger Boost Control B Circuit High
- P004ETurbocharger/Supercharger Boost Control A Circuit Intermittent/Erratic
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.