Engine Light - coded as P0033

This came on this morning, after car was stood for 2 days after driving acout 100 metres.  turned straight around and drove home - plugged in, checked the code.  Wiggled and checked visible commections going anywhere near Turbo.

Light has now gone out and car has been driven for 2-3 hrs today with no warning lights, but I'm wondering if anyone has experience of this fault coming and going, and the possible cost of repair should it come back more permanently.