BoilerFaultCodesPotterton E40 Fault Code
The Potterton E40 fault code means: your boiler has detected that a temperature sensor responsible for monitoring water returning to the unit has disconnected or broken, preventing it from running safely.. It appears on 4 Potterton models in our database.
Technical description: Return sensor open circuit. Check cable/connections not damaged. Renew sensor/cable. Check connections on control
What causes the Potterton E40 fault?
This fault occurs when the boiler's control board loses communication with the sensor that monitors water temperature returning from your radiators. This is typically caused by the internal sensor failing due to age or the electrical wiring connecting it to the main board becoming loose or corroded. Because the boiler can no longer monitor these temperatures to prevent overheating, it shuts down as a safety precaution.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Potterton models that show the E40 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Potterton E40 fault code information on this page is sourced and cross-checked against the official Potterton service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026