Actionneur d'ailettes de turbocompresseur défectueux

The device that moves a variable-geometry turbocharger's vanes — either a vacuum diaphragm working against a spring, or an electric motor with its own position feedback.

The single most useful fact about it is commercial rather than technical: on many vehicles it is available separately from the turbocharger, at a fraction of the price. That is easy not to discover, because the code names the turbocharger and a parts lookup for a turbocharger returns a turbocharger. Asking explicitly whether the actuator can be supplied on its own is worth doing before authorising anything.

On a vacuum-operated turbo, test what reaches the actuator before condemning it. A perished hose, a failed vacuum pump or a dead control solenoid all leave the diaphragm with nothing to work against and produce identical symptoms — and all three are trivial by comparison. On an electric actuator, confirm power, ground and a command signal are present first.

A stuck-at-one-end position with no response to commands points here more than at the vanes, because these actuators are generally arranged to fail to a defined default when they lose their drive; a mechanism jammed by carbon usually stops somewhere in between instead.

And whatever is done, the actuator must relearn its end stops afterwards. Skipping that calibration leaves the reported position permanently disagreeing with the command on parts that are now perfectly good, which reliably gets read as a faulty new component.