Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove connector CN2 from the main PCB

Measurement:

Test 1:
Measure the resistance between pin 4 (Blue) and pin 5 (Brown) on connector CN2.
Expect 1 MOhm or greater.
Test 2:
Measure between pin 4 (Blue) and earth.
Expect open circuit.
Test 3:
Measure between pin 5 (Brown) and earth.
Expect open circuit.