Low presure fualt?

Hi.. Ive had a baxi bolier installed for more or part of 5 years and its has been fine but for some reason every other day it drops pressure well below 0.5 of a bar. Im pretty sure there are no air locks any where in the system because it has been working fine, there is a flashing fualt light appering when it goes below the nominal bar pressure, the fault diagram indicates me that it is the pump or its loosing pressure. I was wondering if you could tell me how i would be able to solve this problem??