BoilerFaultCodesMain E09 Fault Code
The Main E09 fault code means: your boiler has lost its electrical connection to the gas supply unit, meaning it cannot ignite to provide heating or hot water.. It appears on 1 Main model in our database.
Technical description: Gas valve connection error
What causes the Main E09 fault?
This fault occurs when the boiler's main control board loses the electrical signal required to operate the gas valve. The most common reason is a loose or damaged wiring connection between these two parts, or an internal electronic failure within the gas valve itself.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Main models that show the E09 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Main E09 fault code information on this page is sourced and cross-checked against the official Main service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026