Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove connector X2 from the PCB

Measurement:

Test 1.
Measure for resistance across pins 1 (brown) and 3 (blue) of connector X2.
Expected resistance 160 Ohms or greater.
Test 2.
Measure for resistance across pin 1 (brown) and a suitable earth connection.
Expected resistance greater than 1Mohm.