resetting the ecu after a new EGR - Boxer Diesel

[oldmanscooby]

Fitted a new EGR, anyone know how to reset the ECU?
Subaru Forester Boxer Diesel 2008

Disconnecting the battery works for two cycles (start & stop) but always errors on the 3rd.
Using a reader I can see the egr gate opening and closing (on the first two cycles) but freezes on the third.

disconnecting clears all errors and the cycle starts again.

Presume there is a way to clear the ecu fully, anyone know?

Thanks