Boost leak from a split or loose charge pipe, hose, clamp or intercooler joint; Faulty or sticking boost control actuator, wastegate or vane mechanism (carbon build-up or seizure when cold); Faulty vacuum or pressure control solenoid, or cracked or disconnected vacuum lines to the actuator; Wiring or connector fault in the boost control actuator, solenoid or boost and pressure sensor circuits; Faulty boost pressure, manifold pressure or intake air temperature sensor giving incorrect readings; Worn or damaged turbocharger or supercharger (shaft play, damaged wheel, internal wear); Outdated or faulty control unit software where the manufacturer has a known fix.

P056F

Cold Start Turbocharger/Supercharger Boost Control B Performance.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
5: AreaVehicle speed, idle control and auxiliary inputs
6F: FaultThe specific fault in that area

What it means

P056F means the engine control unit has found that the second (B) turbocharger or supercharger boost control system is not performing as expected during or just after a cold start. The actual boost, or the actuator's position, did not match the commanded target within the allowed limits. What 'B' refers to depends on the model: it may be the second turbo, the second bank or a second stage.

Symptoms

Engine warning light on
Reduced power or sluggish acceleration, especially when cold
Limp mode or restricted boost
Whistling, hissing or fluttering noises from the intake or turbo area
Black or blue smoke on cold start
Rough or hesitant running during warm-up

Possible causes

Boost leak from a split or loose charge pipe, hose, clamp or intercooler jointlikely
Faulty or sticking boost control actuator, wastegate or vane mechanism (carbon build-up or seizure when cold)likely
Faulty vacuum or pressure control solenoid, or cracked or disconnected vacuum lines to the actuatorlikely
Wiring or connector fault in the boost control actuator, solenoid or boost and pressure sensor circuitspossible
Faulty boost pressure, manifold pressure or intake air temperature sensor giving incorrect readingspossible
Worn or damaged turbocharger or supercharger (shaft play, damaged wheel, internal wear)possible
Outdated or faulty control unit software where the manufacturer has a known fixrare

How to diagnose

Read all stored and pending codes and the freeze frame data, noting coolant and intake temperature, load and boost at the time the code set
Check for related codes such as other boost, sensor, actuator or vacuum faults and deal with those first
Visually inspect the charge air pipes, hoses, clamps, intercooler and intake for splits, oil residue, looseness or damage
Inspect the wiring and connectors to the boost actuator, solenoid and pressure sensors for chafing, corrosion and poor pins
Check the vacuum lines and pump (where fitted) for leaks, kinks and correct routing, as this depends on the model
With a scan tool, compare commanded and actual boost and actuator position on a cold start, and command the actuator to check it moves freely and smoothly
Smoke or pressure test the intake and charge system to find leaks that are not visible
Check the turbo for shaft play, wheel damage and free movement of the wastegate or vane linkage, following the manufacturer's procedure for the engine

How to fix

Repair or replace leaking charge pipes, hoses, clamps or intercooler components
Free off, clean or replace a sticking boost actuator, wastegate or vane mechanism as the design allows
Replace the faulty solenoid or repair damaged vacuum lines
Repair wiring or connector faults, or replace a faulty pressure or temperature sensor
Repair or replace the turbocharger or supercharger if it is mechanically worn or damaged, and find out why it failed, for example oil supply
Update the control unit software only if the manufacturer lists it as a fix for this fault

Can I keep driving?

Medium severity

The car can usually be driven gently for a short time, but power may be limited and a worn turbo could get worse. Have it checked soon, and stop driving if you hear loud grinding or see heavy smoke.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.