Low Service
P1 on Worcester Bosch Greenstar CDi Compact

Your boiler is stuck in a low-power service mode, meaning it will provide heat but won't reach full power or respond to normal temperature demands.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

Technical description

The display shows alternatively the CH flow temperature and P1. The appliance works continuously at the minimum power (see service function 2.F).

What causes this fault?

This issue occurs because a specific service function has been manually activated within the boiler's control menu, often during a maintenance check. It is not caused by a mechanical failure, but rather by the software being told to stay at the lowest possible flame setting to allow an engineer to take accurate readings.

DIY fix possible

Locate the 'Reset' button on the front of the control panel.Press and hold the Reset button for 3 to 5 seconds.Wait for the boiler to restart; the P1 code should disappear, returning the display to a normal temperature reading.

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Related fault codes

P2View →P3View →

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