b1 High

British Gas b1 Fault Code

Also written as B1 — same fault.

The British Gas b1 fault code means: your boiler's main control board cannot communicate with its security chip, preventing the system from starting.. It appears on 1 British Gas 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: Keyed plug not detected.
Typical repair cost £120-280 (including labour)

Engineer required

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

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British Gas models that show the b1 fault code

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

Source

British Gas b1 fault code information on this page is sourced and cross-checked against the official British Gas service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026