High Lockout
E2 on Worcester Bosch Greenstar 30HE

Your boiler has detected a faulty internal temperature sensor, which means it cannot accurately measure how hot the water is and has stopped running 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

CH flow NTC sensor defective.

What causes this fault?

This fault occurs when the sensor responsible for monitoring the temperature of the water leaving your boiler fails or sends an incorrect signal. The most common reason is the electrical component inside the sensor wearing out over time, though it can also be caused by corroded wiring connections or a build-up of heat that has damaged the sensor’s sensitivity.

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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