BoilerFaultCodesWorcester Bosch Fault 51 122 Fault Code
Also written as FAULT51122 — same fault.
The Worcester Bosch Fault 51 122 fault code means: your boiler has detected that the wrong type of temperature sensor has been installed or configured for your hot water cylinder.. It appears on 2 Worcester Bosch models in our database.
Technical description: Collector temperature sensor type used as cylinder temperature sensor (T2).
What causes the Worcester Bosch Fault 51 122 fault?
This fault happens because the boiler’s control board is receiving an electrical signal from a temperature sensor that it doesn't recognize as the correct type for your hot water tank. It usually occurs if the wrong part was fitted during a repair or if the sensor has developed an internal electrical fault that mimics a different component. In some cases, it can also be caused by a glitch in the boiler's internal settings following a power surge.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Worcester Bosch models that show the Fault 51 122 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Worcester Bosch Fault 51 122 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