Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove connector CN4 from the PCB

Measurement:

Test 1.
Measure the resistance between pins 1 and 5 on connector CN4.
Expected resistance approximately 53 Ohms.
Test 2.
Measure the resistance between each of the pins 1, 2, 3 ,4 and 5 to earth.
Expect a resistance of greater than 1 MOhm for each test.
Note.
A reading of O.L on each pin in test 2 is acceptable as this is greater than 1 MOhm.