The following conditions may result in overboost.
One or more wastegates stuck closed
One or more control hoses leaking/disconnected between wastegate diaphragm and wastegate vent solenoid.
Wastegate vent solenoid stuck in vent position
Control hoses to wastegate vent solenoid swapped.
Hose between boost volume and wastegate vent solenoid disconnected.
Not-yet-detected Turbocharger Boost sensor in-range failure.
The boost control system computes a desired boost based on operating conditions. Via the wastegate pneumatic solenoid valve, it varies the boost pressure limit to achieve its desired boost level (measured by the TCB-A sensor). The air charge control regulates the throttle to control the intake manifold pressure (MAP).