Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove connector X18 from the PCB
Disconnect the electrical connection from the pump (main supply)
With the aid of a screwdriver carefully remove the cover (as below)

Measurement:

Measure the resistance between each of the wires
on the pump main supply harness.
Brown to brown
Blue to blue
Earth to earth
Expect continuity / zero resistance on each wire.
Also visually inspect the condition of the harness.
Note:
Ensure a good connection is made or misdiagnosis may occur.