BoilerFaultCodesWorcester Bosch 2 flashes Fault Code
Also written as 2FLASHES — same fault.
The Worcester Bosch 2 flashes fault code means: your boiler has detected that there isn't enough water circulating through the system, which is preventing it from heating up safely.. It appears on 3 Worcester Bosch models in our database.
Technical description: Pump has run dry.
DIY fix possible
Check the pressure gauge on the front of the boiler; if it is below 1 bar, it needs topping up.Locate the internal or external filling loop and carefully add water until the gauge reads between 1 and 1.5 bar.Bleed any trapped air from your radiators using a radiator key.Reset the boiler to clear the fault code.
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Worcester Bosch models that show the 2 flashes fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Worcester Bosch 2 flashes fault code information on this page is sourced and cross-checked against the official Worcester Bosch service / installation manuals for each affected model.
- Worcester Bosch Greenstar 25CDi manual (PDF)
- Worcester Bosch Greenstar 35 CDi manual (PDF)
- Worcester Bosch Greenstar 42CDi manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026