BoilerFaultCodesWorcester Bosch D4341 Fault Code
The Worcester Bosch D4341 fault code means: your boiler is overheating because water is not moving through the system quickly enough to carry the heat away.. It appears on 1 Worcester Bosch model in our database.
Technical description: Primary flow temperature rising too fast
What causes the Worcester Bosch D4341 fault?
This fault occurs when the water inside the boiler heats up much faster than the system can pump it away. It is usually caused by a failing pump that isn't pushing water effectively or a internal blockage, such as sludge or limescale, that is restricting the flow. When the sensors detect this rapid heat spike, the boiler shuts down to prevent internal damage or melting.
This issue often surfaces during the first cold snap of autumn when a pump that has been idle all summer has seized or 'stuck' and cannot restart.
DIY fix possible
Ensure all radiator valves (TRVs) are turned to their highest settingCheck that the boiler pressure is between 1 and 1.5 bar on the gaugeSwitch the electricity to the boiler off and back on again to reset the system
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Gas Safe Register →Worcester Bosch models that show the D4341 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Worcester Bosch D4341 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