The check engine light recently came on in my 2011 Ford Fiesta. I took it to the dealer because the local mechanic said it seemed to be an issue with the catalytic converter, which is under warranty. However, at the service center, they said the issue is with the oil/water separator (part of the PCV system), which is NOT under warranty (conveniently) and that it would cost $800 to repair! Does this seem right? They say that the oil/water separator has a crack in it, which is clearly not a result of anything I did. I imagine that crack has been there for a while, but Ford refuses to accept ownership of the problem.
According to the Ford Parts site the part only cost about $25.00 (USD).
I am not familiar with how to change this part, but it is entirely possible the rest of the amount quoted is for labor and ancillary parts (gaskets, etc.) to complete the job.
It might be a good idea to contact the local mechanic again. Explain what the dealer found and see what they would charge to replace it.