-II- Low

British Gas -II- Fault Code

Also written as II — same fault.

The British Gas -II- fault code means: your boiler is currently running a routine startup sequence to fill its internal safety trap with water and is not actually faulty.. It appears on 1 British Gas model in our database.

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

Technical description: trap filling programme is active
Typical repair cost £0 (including labour)

DIY fix possible

Wait approximately 15 to 20 minutes for the sequence to finish automaticallyEnsure your thermostat is calling for heatMonitor the display until the code disappears and the boiler starts normal operation

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British Gas models that show the -II- fault code

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

Source

British Gas -II- 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