P2CB7: Turbocharger/Supercharger B Boost Pressure Not Detected – Mechanical

What it means

The boost pressure on branch B is not detected during operation. Mechanical fault — turbo seized, charge pipe disconnected, or wastegate fully open.

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test
• The engine or gearbox may go into limp mode

How it works

The branch B turbocharger or supercharger should produce boost as engine load rises. This mechanical fault code sets when the control module detects no boost pressure on branch B during operation, which can happen if the turbo is seized, a charge pipe has disconnected or the wastegate is stuck open.

Common causes

Most likely first.

1. Turbocharger B seized
2. Charge pipe disconnected

Symptoms

• Check engine light on
• Significant power loss / limp mode
• Possible blue or black smoke from exhaust
• Whistling or hissing sound from intake

How to diagnose it

1. Use freeze-frame and live data to confirm branch B boost remains absent when boost is commanded.
2. With the engine off and cool, inspect branch B charge pipes and couplings for a disconnected or split section.
3. Check the branch B wastegate and actuator linkage for a position that leaves the bypass open or for obvious mechanical damage.
4. Inspect the turbocharger for signs of damage or oil leakage, and check for abnormal shaft drag only using an appropriate service procedure.
5. If the charge path and wastegate are intact, test the branch B turbo mechanically and compare control readings with the manufacturer's specification.

Common fixes

• Reconnect and secure a detached branch B charge pipe.
• Replace a split or damaged charge-air pipe or coupling.
• Repair a stuck or damaged wastegate mechanism if serviceable.
• Replace the branch B turbocharger if testing confirms it is seized or mechanically failed.

Can I keep driving?

Drive only gently to a safe location if the engine runs normally; avoid acceleration, hills and towing because branch B is producing no boost and power may be severely limited. Stop if smoke increases, unusual turbo noises develop or the vehicle cannot maintain safe speed.