High Lockout
L9 on Ideal Logic+ System

Your boiler's internal computer has forgotten its settings or has developed a technical communication error, meaning it cannot safely control the heating process.

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

Printed circuit board (PCB) unconfigured or fault

What causes this fault?

This fault occurs when the boiler's central control board loses its identity or suffers a data communication failure, preventing it from managing the gas valve and pumps. The most common reason is a hardware failure within the motherboard or a missing configuration chip, which acts like a memory card telling the boiler exactly which model it is. It can also be triggered by a sudden power surge or electrical interference that corrupts the board's stored settings.

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

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