Question about Renault Kangoo 1.5dci Turbo

It's for my brothers van, he said one day the turbo just wasn't kicking in any more. It also used to make quite a high pitched whine that got higher as the revs increase.



Now you can just about hear the whine but not as prominent, so it must still be spinning to let air through but it has no oomph as if the turbo wasn't there.



So is the turbo the problem and needs replacing, or could it be something else like the actuator or a sensor?



I'm not much of a pro on turbo's...

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