40 High

British Gas 40 Fault Code

The British Gas 40 fault code means: your boiler has detected an internal electronic failure or a communication error between its main control components.. 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: Heat output: 11.0 kW | Heat input: 11.1 kW | Gas vol. flow rate: 19.4 (l/min at tV/tR = 80/60°C)
Typical repair cost £180-450 (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 40 fault code

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

Source

British Gas 40 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