BoilerFaultCodesIdeal LO2 Fault Code
The Ideal LO2 fault code means: your boiler is likely unable to drain away the condensation it produces naturally, causing it to 'choke' and shut down.. It appears on 3 Ideal models in our database.
Technical description: If the appliance is restarted it will make a gurgling noise prior to locking out
What causes the Ideal LO2 fault?
This fault occurs when the wastewater produced during the heating process cannot flow out of the boiler, causing the internal trap to overflow. The most common reason is a blockage in the external pipework, which prevents the unit from draining and effectively drowns the burner. This backup of water triggers a safety sensor to shut the system down to prevent internal damage.
This fault is extremely common during freezing winter temperatures, as the external condensate pipe can freeze solid and create a backup of water.
DIY fix possible
Locate the plastic pipe leading from the boiler to your outside drain.If it is freezing cold outside, gently pour warm (not boiling) water over the outdoor section of this pipe to melt any ice blockages.Restart the boiler by pressing the reset button.
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Gas Safe Register →Ideal models that show the LO2 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Ideal LO2 fault code information on this page is sourced and cross-checked against the official Ideal service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026