صمام تحويل الشاحن التوربيني عالق

The valve switching between turbochargers or between stages of a sequential system, seized. Sequential arrangements use a small turbocharger low down and a larger one higher up, and this valve directs flow between them.

Stuck in the low-speed position, the engine builds boost quickly and runs out at the top; stuck in the high-speed position it is lazy low down and strong once spinning. That asymmetry across the rev range is the signature and no fuelling fault reproduces it. The valve sits in the exhaust stream, so carbon on the spindle and corrosion in the bore are what hold it. Disconnect the actuator and move the valve by hand — a seized valve and a failed actuator produce the same code and want different repairs.