Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove the pump DC connector from the PCB

Measurement:

Test1:
Measure the resistance between the Purple and White wires
Expect approximately 37 MOhms or greater
Test2:
Measure the resistance between each of the wires and earth.
Expect open circuit on each test.