P02CB

What it means

P02CB means the engine control unit has detected that the boost pressure on the second (B) turbocharger or supercharger is lower than the commanded target. This applies to twin-turbo, sequential or compound setups, or engines with two boosting devices. The ECU compares actual boost from its pressure sensor(s) with the requested value and sets the code when the shortfall persists beyond a calibrated limit and time.

Symptoms

• Noticeable loss of power, especially under load or acceleration
• Engine management light on, possibly with limp mode or reduced power
• Turbo lag or boost that builds late or not at all
• Whistling, hissing or fluttering noises from the intake or turbo area
• Black or blue smoke or increased fuel consumption
• Poor towing or hill-climbing performance

Possible causes

• Boost leak from a split, loose or disconnected charge air pipe, hose, clamp or intercooler joint on the B sidelikely
• Faulty or sticking boost control device on turbo B, such as a wastegate actuator, variable geometry vanes or their control solenoid or electric actuatorlikely
• Vacuum line leak or fault in the vacuum supply or control to the actuatorpossible
• Faulty boost pressure sensor or MAP sensor, or damaged wiring and connectors giving wrong readingspossible
• Restricted airflow or exhaust, such as a blocked air filter, blocked catalyst or particulate filter, or exhaust leak before the turbopossible
• Worn or damaged turbocharger (shaft play, damaged compressor or turbine wheel, oil starvation)possible
• Diverter or recirculation valve stuck open or leakingrare

How to diagnose

1. Read all stored and pending codes and note freeze frame data (load, rpm, boost, temperature) to see when the fault occurs; check for related codes on the other turbo or sensors
2. Confirm which turbo is B for this model and engine, as the layout varies; check the manufacturer's information
3. Visually inspect the air filter, charge air pipes, clamps, intercooler and hoses for splits, oil residue, looseness or damage
4. Inspect wiring and connectors to the boost sensor and actuator or solenoid for damage, corrosion or chafing
5. Check vacuum lines and the vacuum supply for cracks, disconnections or weak vacuum where the system is vacuum operated
6. Compare requested and actual boost on a scan tool during a road test or load test, and compare with the other turbo's readings
7. Command the actuator, solenoid or vanes with a scan tool and check that they move freely and respond; check the diverter valve operation
8. Pressure test the charge air system for leaks, and inspect the turbo for shaft play, wheel damage and oil leaks; check the exhaust for leaks or restriction

How to fix

• Repair or replace leaking charge air pipes, hoses, clamps or intercooler, and refit connections securely
• Replace or free off a faulty wastegate actuator, variable geometry mechanism or boost control solenoid, then carry out any required adaptation or relearn
• Repair vacuum lines or the vacuum supply to the actuator
• Repair wiring or replace a faulty boost pressure or MAP sensor
• Replace a blocked air filter and fix any exhaust restriction or leak causing the underboost
• Repair or replace the turbocharger if worn or damaged, and first find and correct the cause, such as oil supply or contamination

Can I keep driving?

Nearby codes

• P02CAGenericTurbocharger/Supercharger B Overboost Condition
• P02CCGenericCylinder 1 Fuel Injector A Offset Learning At Min Limit