Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Disconnect connector X12 from the PCB

Measurement:

Test 1:
Measure the resistance between the brown and blue wires on the disconnected plug.
Resistance should be approximately 155 Ohms or greater.
Test 2:
Measure the resistance between the brown and the earth wire on the disconnected plug.
Resistance should be at least 1M Ohm.