High Lockout
604 on Worcester Bosch Greenstar 8000 Life/Style

Your boiler has stopped working because its internal computer has detected a communication error with the burner control system.

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

System fault burner control unit

What causes this fault?

This fault occurs when the boiler's main control centre loses its ability to 'talk' to the components that manage the gas burner. It is typically caused by a physical break in the internal wiring or a critical failure within the printed circuit board itself, preventing the boiler from firing safely. Essentially, the boiler has shut down because its internal systems can no longer coordinate the ignition process.

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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