BoilerFaultCodesWhat the manual says
Manufacturer manualPart of the self-test sequence sequence when the appliance is switched on.
What causes this fault?
This occurs when the boiler is performing a routine electronic check of its internal components immediately after being powered on. It is a programmed safety sequence designed to ensure all sensors and controls are responding correctly before the burner ignites. Most often, the code will clear itself within seconds once the software confirms the system is safe to operate.
This code may be seen more frequently following a power cut, which are more common during stormy winter weather.
DIY fix possible
Wait up to 10 minutes for the self-test to completeEnsure the power cycles correctly if you have recently turned the boiler off and onMonitor the display to see if it transitions to a normal temperature reading
Avoid the next call-out bill
A cover plan would handle faults like P4: no call-out fees, no surprise bills.
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Related fault codes
All 38 fault codes on the Greenstar 25HE
Seeing a different code? Every code this model can display, in one place.