I started getting code P171 which could have been a multitude of failed parts like an expensive O2 sensor. Deciding to replace the PCV wasn't so much about the least expensive part as it was more about solving another Rover issue, a strange knocking/ticking engine noise. This part is great, but don't forget to replace the O ring in the quick connector that attaches to the top of this new part, otherwise you will still get the P171 code