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:

Test 1:
Measure the resistance between pin 2 and 3 on connector X3.
Expect approximately 160 ohms or greater.
Test 2:
Measure the resistance between pin 2 and the earth at the incoming mains supply.
Expect a resistance greater than 1Mohm.
Are the resistances as expected?