High Lockout
B7257 on Worcester Bosch GB162

Your boiler's internal computer or its identification chip has developed a communication failure, preventing the system from operating.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

The burner control unit or the KIM (boiler identification module) is faulty

What causes this fault?

This fault occurs when the boiler's main control board loses its connection with the internal memory chip that identifies the specific model and power settings. The most common reason is an electronic component failure within the circuit board or the small module that stores the boiler's unique configuration. Without this data link, the boiler can no longer safely coordinate the heating process and shuts down as a precaution.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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