Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove connector M1 from the PCB

Measurement:

Test 1:
Measure the resistance between pins 8 and 15 on connector M1.
Expect a resistance of approximately 160 Ohms or greater.
Test 2:
Measure the resistance between pin 15 on connector M1 and a suitable earth.
Expect a resistance of 1 Mohm or greater.
Are the resistances measured as expected?