Faulty turbocharger

The turbocharger at fault as an assembly — bearings, wheels, or its integrated actuator — rather than any of the specific failures the corpus lists separately. It is the general case, and it should be the conclusion rather than the starting point, because a leak, a wastegate, a restriction or a sensor all produce the same boost codes far more often.

Establish it physically before accepting it. Shaft play beyond specification, oil in the housings, wheel tips that have contacted, or audible bearing noise. A turbocharger that spins freely, holds its shaft and shows clean housings is not the fault whatever the boost reading says, and the search should move to the pipework, the wastegate and the exhaust.

Where it is genuinely at fault, find out why. Oil starvation from a blocked or coked feed pipe, contamination from degraded oil, or foreign object damage from an intake leak account for most turbocharger failures. Fitting a replacement to the same cause destroys it too, sometimes within weeks, so check the oil feed and drain and inspect the intake tract for debris before the new unit goes on.