BoilerFaultCodes 12 Emergency
Grant 12 Fault Code
The Grant 12 fault code means: your boiler is detecting that exhaust fumes are not properly contained, which means there is a potential risk of dangerous gases escaping into your home environment.. It appears on 10 Grant models in our database.
Technical description: Combustion fumes smell. Check boiler cleaning cover and seal are correctly fitted. Check burner is correctly fitted onto flange. Check flue is correctly sealed into flue outlet of boiler. Check the condensate pipe and trap are operating correctly.
Typical repair cost £120-250 (including labour)
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Grant models that show the 12 fault code
Click a model for the full fault code list and model-specific repair notes.
- Euroflame Repair: £150-300
- Euroflame Condensing Repair: £90-180
- Vortex Repair: £120-250
- Vortex / Eco / Pro Repair: £120-250
- Vortex 15-20 Repair: £120-250
- Vortex 20-26 Repair: £120-250
- Vortex Eco Repair: £120-250
- Vortex Eco External Floor Standing Repair: £120-250
- Vortex Pro Repair: £120-250
- Vortex Pro 15-26 Repair: £120-250
Source
Grant 12 fault code information on this page is sourced and cross-checked against the official Grant service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026