B1
FAULT CODE
Viessmann
Coding Plug Missing
High Severity
Engineer Required
The boiler's coding plug is missing or not read correctly. The boiler cannot verify its configuration.
Step-by-Step Fix Guide
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Step 1
A Gas Safe engineer will need to check the coding plug is fitted correctly
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Step 2
The plug may need reseating or replacing
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Step 3 Engineer only
The boiler will not operate without a valid coding plug
Gas Safe Reminder
Work on gas appliances must be carried out by a Gas Safe registered engineer. The steps above cover safe checks a homeowner can perform - any internal component replacement requires a qualified professional. If in doubt, always call an engineer.