We may have found other answers which could help you.
Click here for Boiler Valliant Fault
No hot water [Valliant boiler, Turbomax VUW 242]?
another with a Valliant showing F22 and 0.4 bar fault?
Vallliant F75 error message?
Valliant Turbo Max Non Condensing RS boiler?
Vallient boiler showing f28 but pressure is fine?
VCW GB 242 EH Valliant Boiler?