Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Disconnect connector M3 from the PCB and make safe
Selector switch in DHW & CH position
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Does the boiler now enter standby or
does the pump still run with no demand?