High
275 on Worcester Bosch 1000

Your boiler has accidentally been left in a restricted diagnostic mode used by engineers during installation, meaning it cannot currently heat your home or water.

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

Boiler electronics in test mode

What causes this fault?

Test mode active

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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