The information on Boiler Decoder is provided for general information only. It is intended to help you understand what a boiler fault code usually means and whether a problem is likely to need an engineer. It is not professional advice and it is not a diagnosis of your boiler.
Codes vary by model and software
Manufacturers do not always use the same code for the same fault across their range. A code can mean different things on different models, on older and newer versions of the same model, or after a software update. We say where we know meanings differ, but we cannot cover every variation. Always check the user manual for your exact boiler model, which is usually available free from the manufacturer's website.
Never work on gas appliances yourself
The only steps we suggest are simple checks that manufacturers expect homeowners to carry out, such as checking the pressure gauge, topping up through the filling loop, pressing reset or thawing a frozen condensate pipe. Never remove the boiler casing or attempt to repair gas, electrical or flue parts. In the UK, work on gas appliances must by law be carried out by a Gas Safe registered engineer. If a reset does not clear a fault after two or three attempts, stop and call an engineer.
If you smell gas: do not use light switches or anything that could cause a spark, open doors and windows, turn off the gas at the meter if you can do so safely, leave the property and call the National Gas Emergency Service on 0800 111 999. In Northern Ireland, call 0800 002 001.
Carbon monoxide warning
A faulty boiler, flue or other fuel-burning appliance can produce carbon monoxide, a poisonous gas you cannot see, smell or taste. Symptoms include headaches, dizziness, nausea, tiredness, breathlessness and confusion, and they often ease when you leave the home. If you suspect carbon monoxide, turn off the appliance if safe to do so, open windows, get everyone outside, call the gas emergency number above and seek medical advice. Every home with a fuel-burning appliance should have a working carbon monoxide alarm.
Prices are typical ranges
Repair and service costs on this site are typical UK ranges, given as a rough guide. They are not quotes. Actual prices depend on your boiler, the parts needed, where you live and the engineer you use. Always get a written quote before work starts.
No affiliation with manufacturers
Boiler Decoder is independent. We are not affiliated with, endorsed by or sponsored by Vaillant, Worcester Bosch, Ideal, Baxi or any other manufacturer. Brand and model names are trademarks of their respective owners and are used only to identify the products we describe.
Advertising disclosure
This site is funded by advertising, including ads served by Google AdSense. We may also use affiliate links in future and will make it clear when we do. Advertising never influences our safety advice. An ad appearing on this site is not an endorsement of the product or company.
Use at your own risk
We take care to keep our content accurate, but we cannot guarantee it is complete or up to date for every boiler. You use the information on this site at your own risk, and to the extent permitted by law we accept no liability for any loss or damage arising from it. For more detail, see our terms of use. If you spot a mistake, please let us know.