High Lockout
E2 on Worcester Bosch Greenstar 12i System

Your boiler has detected a fault with the internal sensor that monitors the temperature of the water heading to your radiators, 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

Flow temperature sensor disconnected

What causes this fault?

This fault occurs when the internal sensor responsible for tracking the temperature of the water leaving the boiler fails to send a clear signal to the control board. The most common reason is that the sensor has physically degraded over time or developed an electrical short, meaning the boiler can no longer safely regulate its heat output.

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

E9View →A1View →C6View →

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