Biasi boiler M90f.28s, thatwon't fire up!?

my combi boiler will give me dhw okish but the water temp knob and therefore the volume of gas to the jets receive only seems to work sporadically resulting in kukewarm water. In addition the boiler will not fire up the central heating at all and doesn't even attempt to do so ,there's is a fault light showing (rapid flashing) could it be the pcb?