Powertrain, generic · Fuel and air metering (injector circuit)

P02CB Turbocharger/Supercharger B Underboost Condition

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

Turbocharger B is a second, separately controlled turbo – on twin-turbo or two-stage systems, or one per bank. No manufacturer using the turbo B codes was found; twin-turbo engines such as GM's 3.0 V6 and Ford's 3.5 EcoBoost report boost faults under P0234/P0299 with a shared boost sensor, so the description follows CARB and the turbo A codes. P02CB means actual boost of turbo B stays below target although the control demands more; for turbo A, GM uses 30–55 kPa (petrol) or 10–50 kPa (diesel). Typical causes are a charge air leak on that side, a wastegate stuck open or a worn turbo. Power is then limited.

Likely causes

Charge air leak (hose, cooler, clamp) on side B
Wastegate B stuck open or control valve faulty
Turbo B worn (bearing play, compressor wheel)
Exhaust leak ahead of turbine B

Symptoms

  • Check engine light on
  • Clear lack of power
  • Whistling with a leak, limp mode

Repair estimate

DifficultyHardWorkshop job
Parts and labour€50–2,000
Time0.5–6 h

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

Parts involved

turbocharger bwastegate bcharge air hoses

Related codes

P0299P02CAP0234P0236P2261

References: law.cornell.edu, gsi.ext.gm.com, gsi.ext.gm.com.