BoilerFaultCodesIdeal L09 Fault Code
The Ideal L09 fault code means: your boiler's internal computer brain is not communicating correctly with the rest of the unit and needs to be officially set up.. It appears on 3 Ideal models in our database.
Technical description: Unconfigured PCB
What causes the Ideal L09 fault?
This fault occurs when the boiler's main control board has lost its identity or was never properly told which specific model it is installed in. The most common reason is that a new circuit board has been fitted but not yet programmed with the correct software code, or a sudden power surge has wiped the board's internal memory.
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 →Ideal models that show the L09 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Ideal L09 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