LD4 High

Biasi LD4 Fault Code

The Biasi LD4 fault code means: your boiler's internal computer brain is reporting a critical communication or hardware failure, meaning the system cannot safely operate.. It appears on 1 Biasi model in our database.

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
Typical repair cost £280-£450 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Biasi models that show the LD4 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Biasi LD4 fault code information on this page is sourced and cross-checked against the official Biasi service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026