BoilerFaultCodesVokera E09 Fault Code
The Vokera E09 fault code means: your boiler has detected that either a temperature sensor in the exhaust pipe is faulty or the main heating component is becoming blocked and dirty.. It appears on 6 Vokera models in our database.
Technical description: Flue thermistor fault or heat exchanger needs cleaning
What causes the Vokera E09 fault?
This fault occurs when the internal safety sensors detect that the exhaust gases are becoming too hot, which is often a sign that heat isn't being transferred efficiently to your water. The most common reason is a buildup of debris and carbon deposits inside the main heat exchanger, which restricts airflow and causes the unit to overheat. In some cases, the sensor itself may have simply failed or developed a loose connection, sending an incorrect reading to the control board.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Vokera models that show the E09 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Vokera E09 fault code information on this page is sourced and cross-checked against the official Vokera service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026