High Lockout
1.E on Worcester Bosch Greenstar CDi Compact

Your boiler's internal pump is detecting a communication error or is set to the wrong operating mode, meaning it cannot circulate water properly.

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

Pump switch mode

What causes this fault?

This fault occurs when the boiler's control board loses touch with the internal pump or notices it is running in the wrong setting. The most common reason is an electronic communication failure between the pump and the main computer, often caused by a loose connection or a failing pump motor. Without this connection, the boiler cannot safely move hot water around your system, so it shuts down to prevent overheating.

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

C1View →C6View →E9View →

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