Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Remove the DC pump connector from the PCB and make safe
Remove vent screw from pump.
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Does the Pump now run?
Note:
Ensure any water released from the vent screw is safely contained and cannot come into contact with the boilers electrics.