High Lockout
E45 on Keston C36

Your boiler has detected an electrical fault with the sensor that monitors exhaust gases, causing the system to shut down for safety.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

Flue sensor short circuit – check connections to flue sensor

What causes this fault?

This fault occurs when the electrical signal from the exhaust gas sensor becomes interrupted, usually because the component has failed internally or the wiring has become damaged. The sensor is designed to monitor the temperature of the fumes leaving your home, and if it detects an electrical short, the boiler will shut down immediately to prevent potential overheating or safety risks.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Related fault codes

E05View →E44View →

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