Technical Service Bulletin

Issue:  DHW and external heat demand not working

Applies to:  Vitodens 200, WB2B Series (all models)

Vitodens 200, WB2B

Important Disclaimer

The information in this bulletin is intended exclusively for licensed heating contractors, and is NOT intended for the end user. This material is NOT intended to take the place of the information contained in the manuals shipped with the product.

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Boiler operates in relay test mode.
DHW pump is not starting on a DHW call.
External heat demand is on but the boiler is not starting.
Fault "CE" is displayed, or coding address "2E" is set to "0".


No communication between the Power Pump Module and the boiler control through the KM-Bus plug 145.


Check the 145 plug connection on the boiler control and in the Power Pump Module.

Re-check coding address "2E". If the value at address "2E" has not changed to "1", then turn power off to the boiler and Power Pump Module. Remove the 145 plug from the boiler control, and cut off the plug. Then reconnect the blue wire to X3 terminal 6, and the brown wire to X3 terminal 7. (This is another connection point for the KM-Bus.)

Turn the power back on for the boiler and Power Pump Module, and check coding address "2E" again – it should be set to "1". Now the boiler should be communicating with the Power Pump Module.

Viessmann Technical Services 

Bulletin ID:     TSB-002

Date issued:   Oct 4, 2016

Updated on:   Jan 11, 2018

Revision #:      02