High Lockout
D1241 on Worcester Bosch GB162

Your boiler has lost its connection to the sensor that monitors the water returning to the unit, causing it to stop working 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

The contacts of the boiler return temperature sensor have been interrupted

What causes this fault?

This fault occurs when the main control board loses communication with the sensor that monitors the temperature of the water coming back into the boiler. The most common reason is that the sensor itself has developed an internal electrical failure or the wiring connecting it to the brain of the boiler has become loose or damaged.

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

D1 240View →

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