BoilerFaultCodesWorcester Bosch 51122 Fault Code
The Worcester Bosch 51122 fault code means: your boiler is confused because the wrong type of temperature sensor has been plugged into the system, meaning it can't accurately monitor your hot water cylinder.. It appears on 1 Worcester Bosch model in our database.
Technical description: Incorrect temperature sensor type connected Collector temperature sensor type used as cylinder temperature sensor (T2).
What causes the Worcester Bosch 51122 fault?
This fault occurs when the boiler's control board detects a signal from a temperature sensor that doesn't match the expected specifications for your hot water cylinder. It most commonly happens because an incorrect or incompatible part was installed during a repair, or because an internal electrical fault has caused the sensor to send a confusing signal to the boiler.
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 51122 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Worcester Bosch 51122 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