Engine Light On

[A55]

Need some advice, I have an Alfa Giulietta diesel, owned if for four years now without any issues, preformed quiet well.

Coming home a few weeks ago the engine light came on and a note telling me to check engine, I rang breakdown who advised me to continue home and get it checked out, this I did, it was running fine.

Garage plugged it into their machine and it indicated a (if I remember correctly) a issue with the oil pump linkage valve? something with the oil pump anyway. They cleared the codes, took the car for a long drive and it was fine, better than fine as it preformed a lot better than previously. Two weeks later I was at my parents house when the light came on again, this time my father plugged his cheap OBD reader in and it said I had a oil sensor or switch issue, once again codes were cleared and it ran happily for 10 days, before the light came on again.

Booked it into the garage, they will look at it next Thursday.

I am curious anyone have ideas what it could be?

The light came on both times when I was doing about 30.