While you wait for answers, we may have found some information which could help you.
Click here for Fill Water TapsGreenstar 25 combo boiler?
I have a greenstar 440 displaying d5, I have tried the reset code ?
over pressure?
Worcester bosch Highflow 400 rsf?
Greenstar 24Ri boiler, fast flashing - can I reset?
Worcester Bosch 532/i Combi Boiler?