BoilerFaultCodesWorcester Bosch EH258 Fault Code
The Worcester Bosch EH258 fault code means: your boiler's internal computer or control module has developed a fault and can no longer communicate with the rest of the system.. It appears on 2 Worcester Bosch models in our database.
Technical description: Control box or the heat control module (HCM) is defective – HCM or control box connections need to be checked
What causes the Worcester Bosch EH258 fault?
This fault occurs when the boiler's internal computer chips lose the ability to talk to each other, often due to a physical failure in the circuitry. The most common reason is that the Heat Control Module has worn out or developed a loose connection, meaning the boiler can no longer safely manage the heating process. In some cases, a power surge or general age-related degradation of the main control board is the root cause.
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 EH258 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Worcester Bosch EH258 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