BoilerFaultCodesWorcester Bosch 2.b Fault Code
Also written as 2B — same fault.
The Worcester Bosch 2.b fault code means: your boiler has sensed that the water inside is getting too hot too quickly and has shut down as a safety precaution.. It appears on 1 Worcester Bosch model in our database.
Technical description: Max. flow temperature
What causes the Worcester Bosch 2.b fault?
This fault occurs when the water inside your boiler cannot circulate fast enough to carry heat away from the burner, causing the internal temperature to spike instantly. The most common reasons are a failing pump that isn't pushing the water round, or a blockage caused by sludge and debris restricting the flow within the system.
This issue often surfaces during the first cold spell of autumn when the heating is turned back on after sitting idle all summer, which can cause internal pump parts to seize.
DIY fix possible
Check that your radiator valves are fully openEnsure the boiler pressure is between 1 and 1.5 bar on the gaugeCheck if the pump is making a humming sound, which might suggest it is stuck
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Gas Safe Register →Worcester Bosch models that show the 2.b fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Worcester Bosch 2.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