HARDWARE
Wastegate — valve
Definition
A pressure-relief valve that bypasses exhaust gas around the turbine wheel to limit boost. Either internal (built into the turbo housing) or external (separate flange). Controlled by the ECU via a vacuum / boost actuator.
Why workshops care
Wastegate stuck open → boost won't build (P0299 underboost). Wastegate stuck closed → boost runs away (P0234 overboost). Both are common failure modes on aged turbos.