Powertrain, generic · Vehicle speed, idle control and auxiliary inputs

P056F Cold Start Turbocharger/Supercharger Boost Control B Performance

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

CARB requires every element commanded by the cold-start strategy to respond measurably in the commanded direction, with its own codes separate from the general monitoring of the same part. During catalyst heating the boost control is positioned deliberately – diesels close the variable turbine for load and heat, petrol engines open the wastegate so heat reaches the catalyst. P056F is the same check for boost control B – a second charger on twin-turbo or sequential systems, or a second stage. No manufacturer document available to us uses P056F; the Ram 6.7 L with a single charger only lists P056E. The description follows CARB's cold-start rules.

Likely causes

Charger B actuator stiff or faulty
Vacuum or charge air line of charger B leaking
Software or calibration
Boost or position sensor B

Symptoms

  • Check engine light on
  • Rough cold running
  • Otherwise usually unremarkable

Repair estimate

DifficultyHardWorkshop job
Parts and labour€0–2,000
Time0.5–5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

turbocharger actuator bboost pressure sensorengine control module

Related codes

P056EP0299P0234P2563P050A

References: law.cornell.edu, static.nhtsa.gov.