High Lockout
F0 on Keston S30

Your boiler's main control computer is missing a vital activation chip, which means the system cannot start up or provide any heat.

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 Chip Card (BCC) not fitted

What causes this fault?

This fault occurs when the boiler's main control board cannot detect the unique memory chip that tells it how to operate safely. The most common reason is that the chip card has vibrated loose, failed electronically, or was not correctly transferred when a technician replaced the circuit board.

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

F2View →L2View →

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