P004D code meaning
Turbocharger/Supercharger Boost Control B Circuit High
Powertrain system Generic code P00xx codes Check engine light
What P004D means
"Boost control B" is the electrically driven actuator the engine control module uses to set boost pressure: depending on the engine a pulse-width modulated solenoid or vacuum converter at the wastegate, the control valve of variable turbine vanes, or an electric actuator with position feedback. B is the second actuator, for example on the high-pressure turbocharger of a two-stage system or on the second turbocharger; it does not denote cylinder bank 2. This code is set when the voltage at the control output is too high, typically because of a short to battery voltage, so the actuator cannot be driven. Without control the actuator usually falls back to its rest position, which on most engines means low boost; depending on the design too much boost is also possible.
P004D at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyMedium, DIY possible
- Typical labor0.5 to 2.5 hours
- Clears after repairAfter a drive cycle
Symptoms of P004D
- Check engine light on
- Loss of power or reduced power mode
- Weak acceleration, noticeable turbo lag
- Overboost possible in rare cases
Common causes of P004D
- Most likelyHarness chafed, short to battery voltage
- PossibleActuator coil shorted
- PossibleWater in the connector
- Less likelyOutput driver in the engine control module faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Boost control actuator bBoost control actuator wiringEngine control module
What each part of P004D means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 0 | Area: fuel and air metering and auxiliary emission controls. |
| 4D | The exact fault in that area. |
What to do next
- Note P004D and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P004D
What does P004D mean?
P004D means "Turbocharger/Supercharger Boost Control B Circuit High". "Boost control B" is the electrically driven actuator the engine control module uses to set boost pressure: depending on the engine a pulse-width modulated solenoid or vacuum converter at the wastegate, the control valve of variable turbine vanes, or an electric actuator with position feedback. It is a generic code, so it means the same on every make.
Is it safe to drive with P004D?
Drive gently and only to a workshop. With P004D the car can go into limp mode (reduced power) to protect itself.
Will P004D fail an emissions test?
Yes, it can. P004D is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P004D to fix?
Difficulty: medium. A typical repair takes 0.5 to 2.5 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P004D clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.