Boiler will not switch to heating or DHW mode on Vitodens 100 B1KE-199 Replacement BCU and HMU units must be configured prior to installation in Vitocrossal 200 CI2 ViCare registration results in E10 / E12 error Viessmann CI2 O2 Probe Measurement Viessmann CI2 Boiler Cleaning Viessmann CI2 F380 Viessmann Gas Valve Viessmann Venting