Kind of a 'what came first, the chicken or the egg' type question.
Yes, a turbo failure can be a cause or a result of a different failure.
It can also be the cause OF a secondary failure.
First, a compression test should be taken......this 'generally' tells if the engine is mechanically sound......I say generally because a compression test only proves the compression rings and their lands (grooves) are sealing well enough to support combustion, however, the oil control rings can be blown apart and compression can be acceptable.......so this is not a 'end all' test.
If compression is good, the next step in this case is to look at the turbo......off the car.
If the bearing is good, the vanes can be easily rotated with the fingertip with no binding.
If the output side seal has failed, the vanes on the output side will be soaked with oil, the intercooler will have a large quantity of oil accumulated and all the corresponding intake (charge) tubing will be wet with oil, as well as the throttle body and intake manifold.
If the drive side (exaust) seal has failed, it will be coated with white, barbecued oil residue and the inlet side of the catalyst screen will be wet(ish) with oil......however, a very close examination of the exaust ports for oil residue should take place......failed oil rings or lands will leave the same residue.
If the ports are wet, it is unlikely the turbo seal has failed. Unlikely, does not mean absolute though.
Next, the turbo vanes on the exaust side are looked at veeeery closely for any evidence of a blade strike......a dent, a chip, any deformation between blades.
Any evidence of a blade strike means a bit of broken piston was ejected into the exaust and the turbo chewed it up.
Yes, some of the model year 2011 did experience piston failure......some engines have had the pistons replaced with success.
The key is, there is no acceptable bore damage from a broken piston or ring......any damage requires engine replacement as well as the turbo.
I mentioned a turbo can be a cause of failure:
If a charge side seal fails it starts out as a very small leak.......this accumulates in the intercooler over time.
If you look at the intercooler the charge pipe leading to the throttle body is about five air tubes (rows) above the bottom.
This allows oil to accumulate and with a normal operating engine, should never get high enough to obstruct intake air flow.
If the turbo seal fails on the intake side, the oil level rises rapidly....to the point where air is actually passing through the oil as bubbles causing a rather violent oil storm in there.
In a deep, prolonged throttle application, like you have it almost floored getting onto the highway, the accumulated oil gets drawn all the way to the throttle body and inhaled.......a little bit makes lots of smoke......a little more makes lots of smoke and uncontrolled spark knock, and more than that makes lots of smoke, lots of spark knock, and a moment of hydrolock.
The last two scenarios break piston ring lands and rings.......so, an engine that only needed a turbo replaced, but did not get its intake system cleaned of accumulated oil, ends up being damaged.
Good grief!
I just re read this book.....no wonder my fingers hurt.
Anyways, you can see how this can be a multi horned problem that requires a mechanic to put together every scenario if a successful repair is going to take place.
Sorry if I went too deep.
Rob