P02CB: Turbocharger/Supercharger B Underboost Condition

What does P02CB mean?

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.

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

Symptoms

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

Common causes

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

Likelihood is a general estimate across vehicles; your make and model may differ.