BoilerFaultCodesThe 6 most common faults
Your boiler has detected a communication issue with its internal gas control system and has shut down as a safety precaution.
Why it happens: This fault occurs when the boiler's main computer loses the ability to safely regulate the flow of gas to the burner. It is typically caused by an electrical failure within the gas valve itself or a breakdown in the wiring that carries signals between the valve and the control board. For safety, the system instantly stops operating because it can no longer guarantee the correct amount of fuel is being delivered.
Locate the reset button or dial on the front control panelPress and hold the reset button for 5 secondsWait for the boiler to complete its restart sequence to see if the flame ignites
Your boiler has detected an electrical issue with the gas control system and has shut down as a safety precaution.
Why it happens: This fault occurs when the boiler's main computer loses the ability to correctly control the electrical signal sent to the gas valve. The most common reason is a physical failure of the internal solenoids within the gas valve or a communication break in the wiring connecting it to the control board. For safety reasons, the boiler immediately stops ignition because it can no longer guarantee the precise regulation of gas flow.
Locate the reset button on the boiler control panelPress and hold the reset button for 2-3 secondsWait for the boiler to attempt to restartIf the code persists, contact a Gas Safe registered engineer
Your boiler is having trouble lighting the gas to start the heating process and may need to be restarted.
Why it happens: This fault occurs when the boiler's control system detects that the gas valve is open but it cannot successfully establish or sense a flame. The most common reasons are a physical failure of the gas valve mechanism, worn-out ignition electrodes that can no longer produce a strong spark, or a degraded spark cable that is leaking electricity before it reaches the burner.
Check that your gas emergency control valve is in the 'on' positionCheck if other gas appliances in your home are workingPress the 'Reset' button on the boiler control panel up to three times
Your boiler is struggling to keep the flame steady and will keep trying to restart itself until it succeeds.
Why it happens: This fault occurs when the boiler's internal computer detects an unstable flame that cannot be maintained safely during the ignition process. The most common reasons are a buildup of carbon on the sensing probes or a fluctuating gas supply that prevents the burner from staying lit. It essentially means the boiler is 'knocking at the door' but the flame isn't catching well enough to stay running.
Wait for the boiler to finish its automatic restart cyclesCheck that your gas meter has credit (if applicable)Ensure other gas appliances in your home are working correctly
Your boiler is struggling to light or recognize that a flame has started, causing it to shut down for safety after several failed attempts.
Why it happens: This fault occurs when the boiler's internal sensors fail to detect a stable flame during the startup process. The most common reasons are a worn-out ignition electrode that cannot create a spark or a buildup of carbon on the probe that monitors the flame. In some cases, a blockage in the drainage pipe or a faulty gas valve prevents the burner from staying lit safely.
Check if other gas appliances, like a hob, are working to ensure gas is reaching the propertyCheck that your gas meter is in credit if you use a prepay meterLocate the reset button on the control panel and press it once to attempt a restart
Your boiler is having trouble managing the flame correctly and has locked itself for safety after failing to stabilise.
Why it happens: This fault happens when the boiler's internal sensor detects that the flame is burning inconsistently or not matching the expected safety signals. It is often caused by a worn-out sensing probe that can no longer 'see' the flame clearly, or a gas valve that is failing to deliver the correct amount of fuel to keep the burner stable.
Locate the reset button on your boiler's control panelPress and hold the reset button for at least 5 secondsWait for the boiler to attempt to restart; if the code returns immediately, call a Gas Safe engineer
on the Daikin D2CND
Based on parts cited in our fault code database. Your engineer will confirm what's actually needed after diagnosis.
Call a Gas Safe engineer if…
- You can smell gas or see signs of a leak
- The Daikin shows an Emergency or High severity code
- The boiler keeps locking out after repeated resets
- You've tried the DIY checks and the fault hasn't cleared
- There's visible water leaking from the boiler
- The flame is yellow or orange instead of blue