High
Ignition lockout on Worcester Bosch Greenstar 15i System

Your boiler is failing to light the flame needed to heat your home, so it has locked itself for safety and requires a manual reset.

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.

What the manual says

Manufacturer manual

Slow flash (normally off, flashes on) | Flashing (reset required) | Gas present and at correct pressure. Combustion CO2level. Flue condition. Ignition electrodes / harness / connections. Gas valve (coils 140-190Ω) / low voltage harness connection. Otherwise replace control board.

From this model's manual
Verified against the Worcester Bosch Greenstar I System installation & service manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

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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