Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove white retaining clip and remove
modulating plug from the pump

Measurement:

Check for continuity of each of the 3 wires from
the pump modulating plug to pins 7, 8 and 9
(black white and purple) of HV2.
Expect continuity (zero resistance).