BoilerFaultCodesWorcester Bosch 8.b Fault Code
Also written as 8B — same fault.
The Worcester Bosch 8.b fault code means: your boiler's internal configuration chip has been disconnected or is not being recognised correctly by the control board.. It appears on 1 Worcester Bosch model in our database.
Technical description: Code plug number
What causes the Worcester Bosch 8.b fault?
This fault occurs when the boiler's control board loses communication with a small memory chip called a code plug, which tells the boiler how to operate. The most common reason is a loose connection caused by general vibration over time or a hardware failure within the chip or the main circuit board itself.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Worcester Bosch models that show the 8.b fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Worcester Bosch 8.b fault code information on this page is sourced and cross-checked against the official Worcester Bosch service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026