High
4 flashes on Worcester Bosch Greenstar 25CDi

Your boiler's internal computer brain is unable to recognize a small identifying chip that tells it how to operate safely.

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

Code plug not detected. Insert code plug correctly, test and replace if necessary.

Shared across the Greenstar range
This code is shared by the boilers in this range, which use the same control board. It may not be printed in this exact variant’s 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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Boiler cover options

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All 22 fault codes on the Greenstar 25CDi

Seeing a different code? Every code this model can display, in one place.

2 flashes3 flashes5 flashes6 flashes7 flashes8 flashes9 flashesA7b1C6CH flow NTC sensor defective.Code plug not detected.E2E9F7Fan speed too low.Flame not detected.Internal error.Pump has run dry.Rapid flashesSlow flashes

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