Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove connector CN8 from the PCB
Remove the leads from the APS making a note of their positions

Measurement:

Test 1:
Measure the resistance between pin 5 (grey) on connector CN8
and the grey lead from connector 3 on the APS.
Test 2:
Measure the resistance between pin 6 (grey) on connector
CN8 and the grey lead from connector 1 on the APS.
Note:
For ease use a crocodile clip on the disconnected APS lead.
Expect continuity/zero resistance on both tests.
Also visually check the condition of the harness.