High
LD4 on Biasi Riva Advance M96.24SM

Your boiler's internal computer brain is reporting a critical communication or hardware failure, meaning the system cannot safely operate.

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

Operation light 4 / Internal P.C.B. light

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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Related fault codes

LD1View →LD2View →

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