Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove connector X3 from the PCB

Measurement:

Measure the resistance between the black wire (pin 9) at X3 to the nearest black wire the mains terminal block (refer to picture).
Expect continuity / zero resistance.
Also visually inspect the condition of the harness.
Is the resistance as expected and is the harness in good condition?
Note:
On some appliances the incoming terminal strip is located differently and has been rotated through 180° from the one shown.