Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove connector X20 from the PCB
Disconnect the plug at the inline connector (as shown)

Measurement:

Test 1:
Measure the resistance between pin 1 (black) on the
inline connector and pin 12 (black) on connector X20.
Test 2:
Measure the resistance between pin 2 (black) on the
inline connector and pin 13 (black) on connector X20.
Expect continuity / zero resistance on each wire.
Also visually inspect the condition of the harness.
Note:
Each pin on the PCB connector is numbered.